source: moodle/trunk/fuentes/lib/datalib.php @ 1331

Last change on this file since 1331 was 1331, checked in by jrpelegrina, 3 years ago

Updated to moodle 3.0.3

File size: 70.4 KB
Line 
1<?php
2// This file is part of Moodle - http://moodle.org/
3//
4// Moodle is free software: you can redistribute it and/or modify
5// it under the terms of the GNU General Public License as published by
6// the Free Software Foundation, either version 3 of the License, or
7// (at your option) any later version.
8//
9// Moodle is distributed in the hope that it will be useful,
10// but WITHOUT ANY WARRANTY; without even the implied warranty of
11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12// GNU General Public License for more details.
13//
14// You should have received a copy of the GNU General Public License
15// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
16
17/**
18 * Library of functions for database manipulation.
19 *
20 * Other main libraries:
21 * - weblib.php - functions that produce web output
22 * - moodlelib.php - general-purpose Moodle functions
23 *
24 * @package    core
25 * @copyright  1999 onwards Martin Dougiamas  {@link http://moodle.com}
26 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
27 */
28
29defined('MOODLE_INTERNAL') || die();
30
31/**
32 * The maximum courses in a category
33 * MAX_COURSES_IN_CATEGORY * MAX_COURSE_CATEGORIES must not be more than max integer!
34 */
35define('MAX_COURSES_IN_CATEGORY', 10000);
36
37/**
38  * The maximum number of course categories
39  * MAX_COURSES_IN_CATEGORY * MAX_COURSE_CATEGORIES must not be more than max integer!
40  */
41define('MAX_COURSE_CATEGORIES', 10000);
42
43/**
44 * Number of seconds to wait before updating lastaccess information in DB.
45 *
46 * We allow overwrites from config.php, useful to ensure coherence in performance
47 * tests results.
48 */
49if (!defined('LASTACCESS_UPDATE_SECS')) {
50    define('LASTACCESS_UPDATE_SECS', 60);
51}
52
53/**
54 * Returns $user object of the main admin user
55 *
56 * @static stdClass $mainadmin
57 * @return stdClass {@link $USER} record from DB, false if not found
58 */
59function get_admin() {
60    global $CFG, $DB;
61
62    static $mainadmin = null;
63    static $prevadmins = null;
64
65    if (empty($CFG->siteadmins)) {
66        // Should not happen on an ordinary site.
67        // It does however happen during unit tests.
68        return false;
69    }
70
71    if (isset($mainadmin) and $prevadmins === $CFG->siteadmins) {
72        return clone($mainadmin);
73    }
74
75    $mainadmin = null;
76
77    foreach (explode(',', $CFG->siteadmins) as $id) {
78        if ($user = $DB->get_record('user', array('id'=>$id, 'deleted'=>0))) {
79            $mainadmin = $user;
80            break;
81        }
82    }
83
84    if ($mainadmin) {
85        $prevadmins = $CFG->siteadmins;
86        return clone($mainadmin);
87    } else {
88        // this should not happen
89        return false;
90    }
91}
92
93/**
94 * Returns list of all admins, using 1 DB query
95 *
96 * @return array
97 */
98function get_admins() {
99    global $DB, $CFG;
100
101    if (empty($CFG->siteadmins)) {  // Should not happen on an ordinary site
102        return array();
103    }
104
105    $sql = "SELECT u.*
106              FROM {user} u
107             WHERE u.deleted = 0 AND u.id IN ($CFG->siteadmins)";
108
109    // We want the same order as in $CFG->siteadmins.
110    $records = $DB->get_records_sql($sql);
111    $admins = array();
112    foreach (explode(',', $CFG->siteadmins) as $id) {
113        $id = (int)$id;
114        if (!isset($records[$id])) {
115            // User does not exist, this should not happen.
116            continue;
117        }
118        $admins[$records[$id]->id] = $records[$id];
119    }
120
121    return $admins;
122}
123
124/**
125 * Search through course users
126 *
127 * If $coursid specifies the site course then this function searches
128 * through all undeleted and confirmed users
129 *
130 * @global object
131 * @uses SITEID
132 * @uses SQL_PARAMS_NAMED
133 * @uses CONTEXT_COURSE
134 * @param int $courseid The course in question.
135 * @param int $groupid The group in question.
136 * @param string $searchtext The string to search for
137 * @param string $sort A field to sort by
138 * @param array $exceptions A list of IDs to ignore, eg 2,4,5,8,9,10
139 * @return array
140 */
141function search_users($courseid, $groupid, $searchtext, $sort='', array $exceptions=null) {
142    global $DB;
143
144    $fullname  = $DB->sql_fullname('u.firstname', 'u.lastname');
145
146    if (!empty($exceptions)) {
147        list($exceptions, $params) = $DB->get_in_or_equal($exceptions, SQL_PARAMS_NAMED, 'ex', false);
148        $except = "AND u.id $exceptions";
149    } else {
150        $except = "";
151        $params = array();
152    }
153
154    if (!empty($sort)) {
155        $order = "ORDER BY $sort";
156    } else {
157        $order = "";
158    }
159
160    $select = "u.deleted = 0 AND u.confirmed = 1 AND (".$DB->sql_like($fullname, ':search1', false)." OR ".$DB->sql_like('u.email', ':search2', false).")";
161    $params['search1'] = "%$searchtext%";
162    $params['search2'] = "%$searchtext%";
163
164    if (!$courseid or $courseid == SITEID) {
165        $sql = "SELECT u.id, u.firstname, u.lastname, u.email
166                  FROM {user} u
167                 WHERE $select
168                       $except
169                $order";
170        return $DB->get_records_sql($sql, $params);
171
172    } else {
173        if ($groupid) {
174            $sql = "SELECT u.id, u.firstname, u.lastname, u.email
175                      FROM {user} u
176                      JOIN {groups_members} gm ON gm.userid = u.id
177                     WHERE $select AND gm.groupid = :groupid
178                           $except
179                     $order";
180            $params['groupid'] = $groupid;
181            return $DB->get_records_sql($sql, $params);
182
183        } else {
184            $context = context_course::instance($courseid);
185
186            // We want to query both the current context and parent contexts.
187            list($relatedctxsql, $relatedctxparams) = $DB->get_in_or_equal($context->get_parent_context_ids(true), SQL_PARAMS_NAMED, 'relatedctx');
188
189            $sql = "SELECT u.id, u.firstname, u.lastname, u.email
190                      FROM {user} u
191                      JOIN {role_assignments} ra ON ra.userid = u.id
192                     WHERE $select AND ra.contextid $relatedctxsql
193                           $except
194                    $order";
195            $params = array_merge($params, $relatedctxparams);
196            return $DB->get_records_sql($sql, $params);
197        }
198    }
199}
200
201/**
202 * Returns SQL used to search through user table to find users (in a query
203 * which may also join and apply other conditions).
204 *
205 * You can combine this SQL with an existing query by adding 'AND $sql' to the
206 * WHERE clause of your query (where $sql is the first element in the array
207 * returned by this function), and merging in the $params array to the parameters
208 * of your query (where $params is the second element). Your query should use
209 * named parameters such as :param, rather than the question mark style.
210 *
211 * There are examples of basic usage in the unit test for this function.
212 *
213 * @param string $search the text to search for (empty string = find all)
214 * @param string $u the table alias for the user table in the query being
215 *     built. May be ''.
216 * @param bool $searchanywhere If true (default), searches in the middle of
217 *     names, otherwise only searches at start
218 * @param array $extrafields Array of extra user fields to include in search
219 * @param array $exclude Array of user ids to exclude (empty = don't exclude)
220 * @param array $includeonly If specified, only returns users that have ids
221 *     incldued in this array (empty = don't restrict)
222 * @return array an array with two elements, a fragment of SQL to go in the
223 *     where clause the query, and an associative array containing any required
224 *     parameters (using named placeholders).
225 */
226function users_search_sql($search, $u = 'u', $searchanywhere = true, array $extrafields = array(),
227        array $exclude = null, array $includeonly = null) {
228    global $DB, $CFG;
229    $params = array();
230    $tests = array();
231
232    if ($u) {
233        $u .= '.';
234    }
235
236    // If we have a $search string, put a field LIKE '$search%' condition on each field.
237    if ($search) {
238        $conditions = array(
239            $DB->sql_fullname($u . 'firstname', $u . 'lastname'),
240            $conditions[] = $u . 'lastname'
241        );
242        foreach ($extrafields as $field) {
243            $conditions[] = $u . $field;
244        }
245        if ($searchanywhere) {
246            $searchparam = '%' . $search . '%';
247        } else {
248            $searchparam = $search . '%';
249        }
250        $i = 0;
251        foreach ($conditions as $key => $condition) {
252            $conditions[$key] = $DB->sql_like($condition, ":con{$i}00", false, false);
253            $params["con{$i}00"] = $searchparam;
254            $i++;
255        }
256        $tests[] = '(' . implode(' OR ', $conditions) . ')';
257    }
258
259    // Add some additional sensible conditions.
260    $tests[] = $u . "id <> :guestid";
261    $params['guestid'] = $CFG->siteguest;
262    $tests[] = $u . 'deleted = 0';
263    $tests[] = $u . 'confirmed = 1';
264
265    // If we are being asked to exclude any users, do that.
266    if (!empty($exclude)) {
267        list($usertest, $userparams) = $DB->get_in_or_equal($exclude, SQL_PARAMS_NAMED, 'ex', false);
268        $tests[] = $u . 'id ' . $usertest;
269        $params = array_merge($params, $userparams);
270    }
271
272    // If we are validating a set list of userids, add an id IN (...) test.
273    if (!empty($includeonly)) {
274        list($usertest, $userparams) = $DB->get_in_or_equal($includeonly, SQL_PARAMS_NAMED, 'val');
275        $tests[] = $u . 'id ' . $usertest;
276        $params = array_merge($params, $userparams);
277    }
278
279    // In case there are no tests, add one result (this makes it easier to combine
280    // this with an existing query as you can always add AND $sql).
281    if (empty($tests)) {
282        $tests[] = '1 = 1';
283    }
284
285    // Combing the conditions and return.
286    return array(implode(' AND ', $tests), $params);
287}
288
289
290/**
291 * This function generates the standard ORDER BY clause for use when generating
292 * lists of users. If you don't have a reason to use a different order, then
293 * you should use this method to generate the order when displaying lists of users.
294 *
295 * If the optional $search parameter is passed, then exact matches to the search
296 * will be sorted first. For example, suppose you have two users 'Al Zebra' and
297 * 'Alan Aardvark'. The default sort is Alan, then Al. If, however, you search for
298 * 'Al', then Al will be listed first. (With two users, this is not a big deal,
299 * but with thousands of users, it is essential.)
300 *
301 * The list of fields scanned for exact matches are:
302 *  - firstname
303 *  - lastname
304 *  - $DB->sql_fullname
305 *  - those returned by get_extra_user_fields
306 *
307 * If named parameters are used (which is the default, and highly recommended),
308 * then the parameter names are like :usersortexactN, where N is an int.
309 *
310 * The simplest possible example use is:
311 * list($sort, $params) = users_order_by_sql();
312 * $sql = 'SELECT * FROM {users} ORDER BY ' . $sort;
313 *
314 * A more complex example, showing that this sort can be combined with other sorts:
315 * list($sort, $sortparams) = users_order_by_sql('u');
316 * $sql = "SELECT g.id AS groupid, gg.groupingid, u.id AS userid, u.firstname, u.lastname, u.idnumber, u.username
317 *           FROM {groups} g
318 *      LEFT JOIN {groupings_groups} gg ON g.id = gg.groupid
319 *      LEFT JOIN {groups_members} gm ON g.id = gm.groupid
320 *      LEFT JOIN {user} u ON gm.userid = u.id
321 *          WHERE g.courseid = :courseid $groupwhere $groupingwhere
322 *       ORDER BY g.name, $sort";
323 * $params += $sortparams;
324 *
325 * An example showing the use of $search:
326 * list($sort, $sortparams) = users_order_by_sql('u', $search, $this->get_context());
327 * $order = ' ORDER BY ' . $sort;
328 * $params += $sortparams;
329 * $availableusers = $DB->get_records_sql($fields . $sql . $order, $params, $page*$perpage, $perpage);
330 *
331 * @param string $usertablealias (optional) any table prefix for the {users} table. E.g. 'u'.
332 * @param string $search (optional) a current search string. If given,
333 *      any exact matches to this string will be sorted first.
334 * @param context $context the context we are in. Use by get_extra_user_fields.
335 *      Defaults to $PAGE->context.
336 * @return array with two elements:
337 *      string SQL fragment to use in the ORDER BY clause. For example, "firstname, lastname".
338 *      array of parameters used in the SQL fragment.
339 */
340function users_order_by_sql($usertablealias = '', $search = null, context $context = null) {
341    global $DB, $PAGE;
342
343    if ($usertablealias) {
344        $tableprefix = $usertablealias . '.';
345    } else {
346        $tableprefix = '';
347    }
348
349    $sort = "{$tableprefix}lastname, {$tableprefix}firstname, {$tableprefix}id";
350    $params = array();
351
352    if (!$search) {
353        return array($sort, $params);
354    }
355
356    if (!$context) {
357        $context = $PAGE->context;
358    }
359
360    $exactconditions = array();
361    $paramkey = 'usersortexact1';
362
363    $exactconditions[] = $DB->sql_fullname($tableprefix . 'firstname', $tableprefix  . 'lastname') .
364            ' = :' . $paramkey;
365    $params[$paramkey] = $search;
366    $paramkey++;
367
368    $fieldstocheck = array_merge(array('firstname', 'lastname'), get_extra_user_fields($context));
369    foreach ($fieldstocheck as $key => $field) {
370        $exactconditions[] = 'LOWER(' . $tableprefix . $field . ') = LOWER(:' . $paramkey . ')';
371        $params[$paramkey] = $search;
372        $paramkey++;
373    }
374
375    $sort = 'CASE WHEN ' . implode(' OR ', $exactconditions) .
376            ' THEN 0 ELSE 1 END, ' . $sort;
377
378    return array($sort, $params);
379}
380
381/**
382 * Returns a subset of users
383 *
384 * @global object
385 * @uses DEBUG_DEVELOPER
386 * @uses SQL_PARAMS_NAMED
387 * @param bool $get If false then only a count of the records is returned
388 * @param string $search A simple string to search for
389 * @param bool $confirmed A switch to allow/disallow unconfirmed users
390 * @param array $exceptions A list of IDs to ignore, eg 2,4,5,8,9,10
391 * @param string $sort A SQL snippet for the sorting criteria to use
392 * @param string $firstinitial Users whose first name starts with $firstinitial
393 * @param string $lastinitial Users whose last name starts with $lastinitial
394 * @param string $page The page or records to return
395 * @param string $recordsperpage The number of records to return per page
396 * @param string $fields A comma separated list of fields to be returned from the chosen table.
397 * @return array|int|bool  {@link $USER} records unless get is false in which case the integer count of the records found is returned.
398 *                        False is returned if an error is encountered.
399 */
400function get_users($get=true, $search='', $confirmed=false, array $exceptions=null, $sort='firstname ASC',
401                   $firstinitial='', $lastinitial='', $page='', $recordsperpage='', $fields='*', $extraselect='', array $extraparams=null) {
402    global $DB, $CFG;
403
404    if ($get && !$recordsperpage) {
405        debugging('Call to get_users with $get = true no $recordsperpage limit. ' .
406                'On large installations, this will probably cause an out of memory error. ' .
407                'Please think again and change your code so that it does not try to ' .
408                'load so much data into memory.', DEBUG_DEVELOPER);
409    }
410
411    $fullname  = $DB->sql_fullname();
412
413    $select = " id <> :guestid AND deleted = 0";
414    $params = array('guestid'=>$CFG->siteguest);
415
416    if (!empty($search)){
417        $search = trim($search);
418        $select .= " AND (".$DB->sql_like($fullname, ':search1', false)." OR ".$DB->sql_like('email', ':search2', false)." OR username = :search3)";
419        $params['search1'] = "%$search%";
420        $params['search2'] = "%$search%";
421        $params['search3'] = "$search";
422    }
423
424    if ($confirmed) {
425        $select .= " AND confirmed = 1";
426    }
427
428    if ($exceptions) {
429        list($exceptions, $eparams) = $DB->get_in_or_equal($exceptions, SQL_PARAMS_NAMED, 'ex', false);
430        $params = $params + $eparams;
431        $select .= " AND id $exceptions";
432    }
433
434    if ($firstinitial) {
435        $select .= " AND ".$DB->sql_like('firstname', ':fni', false, false);
436        $params['fni'] = "$firstinitial%";
437    }
438    if ($lastinitial) {
439        $select .= " AND ".$DB->sql_like('lastname', ':lni', false, false);
440        $params['lni'] = "$lastinitial%";
441    }
442
443    if ($extraselect) {
444        $select .= " AND $extraselect";
445        $params = $params + (array)$extraparams;
446    }
447
448    if ($get) {
449        return $DB->get_records_select('user', $select, $params, $sort, $fields, $page, $recordsperpage);
450    } else {
451        return $DB->count_records_select('user', $select, $params);
452    }
453}
454
455
456/**
457 * Return filtered (if provided) list of users in site, except guest and deleted users.
458 *
459 * @param string $sort An SQL field to sort by
460 * @param string $dir The sort direction ASC|DESC
461 * @param int $page The page or records to return
462 * @param int $recordsperpage The number of records to return per page
463 * @param string $search A simple string to search for
464 * @param string $firstinitial Users whose first name starts with $firstinitial
465 * @param string $lastinitial Users whose last name starts with $lastinitial
466 * @param string $extraselect An additional SQL select statement to append to the query
467 * @param array $extraparams Additional parameters to use for the above $extraselect
468 * @param stdClass $extracontext If specified, will include user 'extra fields'
469 *   as appropriate for current user and given context
470 * @return array Array of {@link $USER} records
471 */
472function get_users_listing($sort='lastaccess', $dir='ASC', $page=0, $recordsperpage=0,
473                           $search='', $firstinitial='', $lastinitial='', $extraselect='',
474                           array $extraparams=null, $extracontext = null) {
475    global $DB, $CFG;
476
477    $fullname  = $DB->sql_fullname();
478
479    $select = "deleted <> 1 AND id <> :guestid";
480    $params = array('guestid' => $CFG->siteguest);
481
482    if (!empty($search)) {
483        $search = trim($search);
484        $select .= " AND (". $DB->sql_like($fullname, ':search1', false, false).
485                   " OR ". $DB->sql_like('email', ':search2', false, false).
486                   " OR username = :search3)";
487        $params['search1'] = "%$search%";
488        $params['search2'] = "%$search%";
489        $params['search3'] = "$search";
490    }
491
492    if ($firstinitial) {
493        $select .= " AND ". $DB->sql_like('firstname', ':fni', false, false);
494        $params['fni'] = "$firstinitial%";
495    }
496    if ($lastinitial) {
497        $select .= " AND ". $DB->sql_like('lastname', ':lni', false, false);
498        $params['lni'] = "$lastinitial%";
499    }
500
501    if ($extraselect) {
502        $select .= " AND $extraselect";
503        $params = $params + (array)$extraparams;
504    }
505
506    if ($sort) {
507        $sort = " ORDER BY $sort $dir";
508    }
509
510    // If a context is specified, get extra user fields that the current user
511    // is supposed to see.
512    $extrafields = '';
513    if ($extracontext) {
514        $extrafields = get_extra_user_fields_sql($extracontext, '', '',
515                array('id', 'username', 'email', 'firstname', 'lastname', 'city', 'country',
516                'lastaccess', 'confirmed', 'mnethostid'));
517    }
518    $namefields = get_all_user_name_fields(true);
519    $extrafields = "$extrafields, $namefields";
520
521    // warning: will return UNCONFIRMED USERS
522    return $DB->get_records_sql("SELECT id, username, email, city, country, lastaccess, confirmed, mnethostid, suspended $extrafields
523                                   FROM {user}
524                                  WHERE $select
525                                  $sort", $params, $page, $recordsperpage);
526
527}
528
529
530/**
531 * Full list of users that have confirmed their accounts.
532 *
533 * @global object
534 * @return array of unconfirmed users
535 */
536function get_users_confirmed() {
537    global $DB, $CFG;
538    return $DB->get_records_sql("SELECT *
539                                   FROM {user}
540                                  WHERE confirmed = 1 AND deleted = 0 AND id <> ?", array($CFG->siteguest));
541}
542
543
544/// OTHER SITE AND COURSE FUNCTIONS /////////////////////////////////////////////
545
546
547/**
548 * Returns $course object of the top-level site.
549 *
550 * @return object A {@link $COURSE} object for the site, exception if not found
551 */
552function get_site() {
553    global $SITE, $DB;
554
555    if (!empty($SITE->id)) {   // We already have a global to use, so return that
556        return $SITE;
557    }
558
559    if ($course = $DB->get_record('course', array('category'=>0))) {
560        return $course;
561    } else {
562        // course table exists, but the site is not there,
563        // unfortunately there is no automatic way to recover
564        throw new moodle_exception('nosite', 'error');
565    }
566}
567
568/**
569 * Gets a course object from database. If the course id corresponds to an
570 * already-loaded $COURSE or $SITE object, then the loaded object will be used,
571 * saving a database query.
572 *
573 * If it reuses an existing object, by default the object will be cloned. This
574 * means you can modify the object safely without affecting other code.
575 *
576 * @param int $courseid Course id
577 * @param bool $clone If true (default), makes a clone of the record
578 * @return stdClass A course object
579 * @throws dml_exception If not found in database
580 */
581function get_course($courseid, $clone = true) {
582    global $DB, $COURSE, $SITE;
583    if (!empty($COURSE->id) && $COURSE->id == $courseid) {
584        return $clone ? clone($COURSE) : $COURSE;
585    } else if (!empty($SITE->id) && $SITE->id == $courseid) {
586        return $clone ? clone($SITE) : $SITE;
587    } else {
588        return $DB->get_record('course', array('id' => $courseid), '*', MUST_EXIST);
589    }
590}
591
592/**
593 * Returns list of courses, for whole site, or category
594 *
595 * Returns list of courses, for whole site, or category
596 * Important: Using c.* for fields is extremely expensive because
597 *            we are using distinct. You almost _NEVER_ need all the fields
598 *            in such a large SELECT
599 *
600 * @global object
601 * @global object
602 * @global object
603 * @uses CONTEXT_COURSE
604 * @param string|int $categoryid Either a category id or 'all' for everything
605 * @param string $sort A field and direction to sort by
606 * @param string $fields The additional fields to return
607 * @return array Array of courses
608 */
609function get_courses($categoryid="all", $sort="c.sortorder ASC", $fields="c.*") {
610
611    global $USER, $CFG, $DB;
612
613    $params = array();
614
615    if ($categoryid !== "all" && is_numeric($categoryid)) {
616        $categoryselect = "WHERE c.category = :catid";
617        $params['catid'] = $categoryid;
618    } else {
619        $categoryselect = "";
620    }
621
622    if (empty($sort)) {
623        $sortstatement = "";
624    } else {
625        $sortstatement = "ORDER BY $sort";
626    }
627
628    $visiblecourses = array();
629
630    $ccselect = ', ' . context_helper::get_preload_record_columns_sql('ctx');
631    $ccjoin = "LEFT JOIN {context} ctx ON (ctx.instanceid = c.id AND ctx.contextlevel = :contextlevel)";
632    $params['contextlevel'] = CONTEXT_COURSE;
633
634    $sql = "SELECT $fields $ccselect
635              FROM {course} c
636           $ccjoin
637              $categoryselect
638              $sortstatement";
639
640    // pull out all course matching the cat
641    if ($courses = $DB->get_records_sql($sql, $params)) {
642
643        // loop throught them
644        foreach ($courses as $course) {
645            context_helper::preload_from_record($course);
646            if (isset($course->visible) && $course->visible <= 0) {
647                // for hidden courses, require visibility check
648                if (has_capability('moodle/course:viewhiddencourses', context_course::instance($course->id))) {
649                    $visiblecourses [$course->id] = $course;
650                }
651            } else {
652                $visiblecourses [$course->id] = $course;
653            }
654        }
655    }
656    return $visiblecourses;
657}
658
659
660/**
661 * Returns list of courses, for whole site, or category
662 *
663 * Similar to get_courses, but allows paging
664 * Important: Using c.* for fields is extremely expensive because
665 *            we are using distinct. You almost _NEVER_ need all the fields
666 *            in such a large SELECT
667 *
668 * @global object
669 * @global object
670 * @global object
671 * @uses CONTEXT_COURSE
672 * @param string|int $categoryid Either a category id or 'all' for everything
673 * @param string $sort A field and direction to sort by
674 * @param string $fields The additional fields to return
675 * @param int $totalcount Reference for the number of courses
676 * @param string $limitfrom The course to start from
677 * @param string $limitnum The number of courses to limit to
678 * @return array Array of courses
679 */
680function get_courses_page($categoryid="all", $sort="c.sortorder ASC", $fields="c.*",
681                          &$totalcount, $limitfrom="", $limitnum="") {
682    global $USER, $CFG, $DB;
683
684    $params = array();
685
686    $categoryselect = "";
687    if ($categoryid !== "all" && is_numeric($categoryid)) {
688        $categoryselect = "WHERE c.category = :catid";
689        $params['catid'] = $categoryid;
690    } else {
691        $categoryselect = "";
692    }
693
694    $ccselect = ', ' . context_helper::get_preload_record_columns_sql('ctx');
695    $ccjoin = "LEFT JOIN {context} ctx ON (ctx.instanceid = c.id AND ctx.contextlevel = :contextlevel)";
696    $params['contextlevel'] = CONTEXT_COURSE;
697
698    $totalcount = 0;
699    if (!$limitfrom) {
700        $limitfrom = 0;
701    }
702    $visiblecourses = array();
703
704    $sql = "SELECT $fields $ccselect
705              FROM {course} c
706              $ccjoin
707           $categoryselect
708          ORDER BY $sort";
709
710    // pull out all course matching the cat
711    $rs = $DB->get_recordset_sql($sql, $params);
712    // iteration will have to be done inside loop to keep track of the limitfrom and limitnum
713    foreach($rs as $course) {
714        context_helper::preload_from_record($course);
715        if ($course->visible <= 0) {
716            // for hidden courses, require visibility check
717            if (has_capability('moodle/course:viewhiddencourses', context_course::instance($course->id))) {
718                $totalcount++;
719                if ($totalcount > $limitfrom && (!$limitnum or count($visiblecourses) < $limitnum)) {
720                    $visiblecourses [$course->id] = $course;
721                }
722            }
723        } else {
724            $totalcount++;
725            if ($totalcount > $limitfrom && (!$limitnum or count($visiblecourses) < $limitnum)) {
726                $visiblecourses [$course->id] = $course;
727            }
728        }
729    }
730    $rs->close();
731    return $visiblecourses;
732}
733
734/**
735 * A list of courses that match a search
736 *
737 * @global object
738 * @global object
739 * @param array $searchterms An array of search criteria
740 * @param string $sort A field and direction to sort by
741 * @param int $page The page number to get
742 * @param int $recordsperpage The number of records per page
743 * @param int $totalcount Passed in by reference.
744 * @return object {@link $COURSE} records
745 */
746function get_courses_search($searchterms, $sort, $page, $recordsperpage, &$totalcount) {
747    global $CFG, $DB;
748
749    if ($DB->sql_regex_supported()) {
750        $REGEXP    = $DB->sql_regex(true);
751        $NOTREGEXP = $DB->sql_regex(false);
752    }
753
754    $searchcond = array();
755    $params     = array();
756    $i = 0;
757
758    // Thanks Oracle for your non-ansi concat and type limits in coalesce. MDL-29912
759    if ($DB->get_dbfamily() == 'oracle') {
760        $concat = "(c.summary|| ' ' || c.fullname || ' ' || c.idnumber || ' ' || c.shortname)";
761    } else {
762        $concat = $DB->sql_concat("COALESCE(c.summary, '')", "' '", 'c.fullname', "' '", 'c.idnumber', "' '", 'c.shortname');
763    }
764
765    foreach ($searchterms as $searchterm) {
766        $i++;
767
768        $NOT = false; /// Initially we aren't going to perform NOT LIKE searches, only MSSQL and Oracle
769                   /// will use it to simulate the "-" operator with LIKE clause
770
771    /// Under Oracle and MSSQL, trim the + and - operators and perform
772    /// simpler LIKE (or NOT LIKE) queries
773        if (!$DB->sql_regex_supported()) {
774            if (substr($searchterm, 0, 1) == '-') {
775                $NOT = true;
776            }
777            $searchterm = trim($searchterm, '+-');
778        }
779
780        // TODO: +- may not work for non latin languages
781
782        if (substr($searchterm,0,1) == '+') {
783            $searchterm = trim($searchterm, '+-');
784            $searchterm = preg_quote($searchterm, '|');
785            $searchcond[] = "$concat $REGEXP :ss$i";
786            $params['ss'.$i] = "(^|[^a-zA-Z0-9])$searchterm([^a-zA-Z0-9]|$)";
787
788        } else if (substr($searchterm,0,1) == "-") {
789            $searchterm = trim($searchterm, '+-');
790            $searchterm = preg_quote($searchterm, '|');
791            $searchcond[] = "$concat $NOTREGEXP :ss$i";
792            $params['ss'.$i] = "(^|[^a-zA-Z0-9])$searchterm([^a-zA-Z0-9]|$)";
793
794        } else {
795            $searchcond[] = $DB->sql_like($concat,":ss$i", false, true, $NOT);
796            $params['ss'.$i] = "%$searchterm%";
797        }
798    }
799
800    if (empty($searchcond)) {
801        $totalcount = 0;
802        return array();
803    }
804
805    $searchcond = implode(" AND ", $searchcond);
806
807    $courses = array();
808    $c = 0; // counts how many visible courses we've seen
809
810    // Tiki pagination
811    $limitfrom = $page * $recordsperpage;
812    $limitto   = $limitfrom + $recordsperpage;
813
814    $ccselect = ', ' . context_helper::get_preload_record_columns_sql('ctx');
815    $ccjoin = "LEFT JOIN {context} ctx ON (ctx.instanceid = c.id AND ctx.contextlevel = :contextlevel)";
816    $params['contextlevel'] = CONTEXT_COURSE;
817
818    $sql = "SELECT c.* $ccselect
819              FROM {course} c
820           $ccjoin
821             WHERE $searchcond AND c.id <> ".SITEID."
822          ORDER BY $sort";
823
824    $rs = $DB->get_recordset_sql($sql, $params);
825    foreach($rs as $course) {
826        if (!$course->visible) {
827            // preload contexts only for hidden courses or courses we need to return
828            context_helper::preload_from_record($course);
829            $coursecontext = context_course::instance($course->id);
830            if (!has_capability('moodle/course:viewhiddencourses', $coursecontext)) {
831                continue;
832            }
833        }
834        // Don't exit this loop till the end
835        // we need to count all the visible courses
836        // to update $totalcount
837        if ($c >= $limitfrom && $c < $limitto) {
838            $courses[$course->id] = $course;
839        }
840        $c++;
841    }
842    $rs->close();
843
844    // our caller expects 2 bits of data - our return
845    // array, and an updated $totalcount
846    $totalcount = $c;
847    return $courses;
848}
849
850/**
851 * Fixes course category and course sortorder, also verifies category and course parents and paths.
852 * (circular references are not fixed)
853 *
854 * @global object
855 * @global object
856 * @uses MAX_COURSES_IN_CATEGORY
857 * @uses MAX_COURSE_CATEGORIES
858 * @uses SITEID
859 * @uses CONTEXT_COURSE
860 * @return void
861 */
862function fix_course_sortorder() {
863    global $DB, $SITE;
864
865    //WARNING: this is PHP5 only code!
866
867    // if there are any changes made to courses or categories we will trigger
868    // the cache events to purge all cached courses/categories data
869    $cacheevents = array();
870
871    if ($unsorted = $DB->get_records('course_categories', array('sortorder'=>0))) {
872        //move all categories that are not sorted yet to the end
873        $DB->set_field('course_categories', 'sortorder', MAX_COURSES_IN_CATEGORY*MAX_COURSE_CATEGORIES, array('sortorder'=>0));
874        $cacheevents['changesincoursecat'] = true;
875    }
876
877    $allcats = $DB->get_records('course_categories', null, 'sortorder, id', 'id, sortorder, parent, depth, path');
878    $topcats    = array();
879    $brokencats = array();
880    foreach ($allcats as $cat) {
881        $sortorder = (int)$cat->sortorder;
882        if (!$cat->parent) {
883            while(isset($topcats[$sortorder])) {
884                $sortorder++;
885            }
886            $topcats[$sortorder] = $cat;
887            continue;
888        }
889        if (!isset($allcats[$cat->parent])) {
890            $brokencats[] = $cat;
891            continue;
892        }
893        if (!isset($allcats[$cat->parent]->children)) {
894            $allcats[$cat->parent]->children = array();
895        }
896        while(isset($allcats[$cat->parent]->children[$sortorder])) {
897            $sortorder++;
898        }
899        $allcats[$cat->parent]->children[$sortorder] = $cat;
900    }
901    unset($allcats);
902
903    // add broken cats to category tree
904    if ($brokencats) {
905        $defaultcat = reset($topcats);
906        foreach ($brokencats as $cat) {
907            $topcats[] = $cat;
908        }
909    }
910
911    // now walk recursively the tree and fix any problems found
912    $sortorder = 0;
913    $fixcontexts = array();
914    if (_fix_course_cats($topcats, $sortorder, 0, 0, '', $fixcontexts)) {
915        $cacheevents['changesincoursecat'] = true;
916    }
917
918    // detect if there are "multiple" frontpage courses and fix them if needed
919    $frontcourses = $DB->get_records('course', array('category'=>0), 'id');
920    if (count($frontcourses) > 1) {
921        if (isset($frontcourses[SITEID])) {
922            $frontcourse = $frontcourses[SITEID];
923            unset($frontcourses[SITEID]);
924        } else {
925            $frontcourse = array_shift($frontcourses);
926        }
927        $defaultcat = reset($topcats);
928        foreach ($frontcourses as $course) {
929            $DB->set_field('course', 'category', $defaultcat->id, array('id'=>$course->id));
930            $context = context_course::instance($course->id);
931            $fixcontexts[$context->id] = $context;
932            $cacheevents['changesincourse'] = true;
933        }
934        unset($frontcourses);
935    } else {
936        $frontcourse = reset($frontcourses);
937    }
938
939    // now fix the paths and depths in context table if needed
940    if ($fixcontexts) {
941        foreach ($fixcontexts as $fixcontext) {
942            $fixcontext->reset_paths(false);
943        }
944        context_helper::build_all_paths(false);
945        unset($fixcontexts);
946        $cacheevents['changesincourse'] = true;
947        $cacheevents['changesincoursecat'] = true;
948    }
949
950    // release memory
951    unset($topcats);
952    unset($brokencats);
953    unset($fixcontexts);
954
955    // fix frontpage course sortorder
956    if ($frontcourse->sortorder != 1) {
957        $DB->set_field('course', 'sortorder', 1, array('id'=>$frontcourse->id));
958        $cacheevents['changesincourse'] = true;
959    }
960
961    // now fix the course counts in category records if needed
962    $sql = "SELECT cc.id, cc.coursecount, COUNT(c.id) AS newcount
963              FROM {course_categories} cc
964              LEFT JOIN {course} c ON c.category = cc.id
965          GROUP BY cc.id, cc.coursecount
966            HAVING cc.coursecount <> COUNT(c.id)";
967
968    if ($updatecounts = $DB->get_records_sql($sql)) {
969        // categories with more courses than MAX_COURSES_IN_CATEGORY
970        $categories = array();
971        foreach ($updatecounts as $cat) {
972            $cat->coursecount = $cat->newcount;
973            if ($cat->coursecount >= MAX_COURSES_IN_CATEGORY) {
974                $categories[] = $cat->id;
975            }
976            unset($cat->newcount);
977            $DB->update_record_raw('course_categories', $cat, true);
978        }
979        if (!empty($categories)) {
980            $str = implode(', ', $categories);
981            debugging("The number of courses (category id: $str) has reached MAX_COURSES_IN_CATEGORY (" . MAX_COURSES_IN_CATEGORY . "), it will cause a sorting performance issue, please increase the value of MAX_COURSES_IN_CATEGORY in lib/datalib.php file. See tracker issue: MDL-25669", DEBUG_DEVELOPER);
982        }
983        $cacheevents['changesincoursecat'] = true;
984    }
985
986    // now make sure that sortorders in course table are withing the category sortorder ranges
987    $sql = "SELECT DISTINCT cc.id, cc.sortorder
988              FROM {course_categories} cc
989              JOIN {course} c ON c.category = cc.id
990             WHERE c.sortorder < cc.sortorder OR c.sortorder > cc.sortorder + ".MAX_COURSES_IN_CATEGORY;
991
992    if ($fixcategories = $DB->get_records_sql($sql)) {
993        //fix the course sortorder ranges
994        foreach ($fixcategories as $cat) {
995            $sql = "UPDATE {course}
996                       SET sortorder = ".$DB->sql_modulo('sortorder', MAX_COURSES_IN_CATEGORY)." + ?
997                     WHERE category = ?";
998            $DB->execute($sql, array($cat->sortorder, $cat->id));
999        }
1000        $cacheevents['changesincoursecat'] = true;
1001    }
1002    unset($fixcategories);
1003
1004    // categories having courses with sortorder duplicates or having gaps in sortorder
1005    $sql = "SELECT DISTINCT c1.category AS id , cc.sortorder
1006              FROM {course} c1
1007              JOIN {course} c2 ON c1.sortorder = c2.sortorder
1008              JOIN {course_categories} cc ON (c1.category = cc.id)
1009             WHERE c1.id <> c2.id";
1010    $fixcategories = $DB->get_records_sql($sql);
1011
1012    $sql = "SELECT cc.id, cc.sortorder, cc.coursecount, MAX(c.sortorder) AS maxsort, MIN(c.sortorder) AS minsort
1013              FROM {course_categories} cc
1014              JOIN {course} c ON c.category = cc.id
1015          GROUP BY cc.id, cc.sortorder, cc.coursecount
1016            HAVING (MAX(c.sortorder) <>  cc.sortorder + cc.coursecount) OR (MIN(c.sortorder) <>  cc.sortorder + 1)";
1017    $gapcategories = $DB->get_records_sql($sql);
1018
1019    foreach ($gapcategories as $cat) {
1020        if (isset($fixcategories[$cat->id])) {
1021            // duplicates detected already
1022
1023        } else if ($cat->minsort == $cat->sortorder and $cat->maxsort == $cat->sortorder + $cat->coursecount - 1) {
1024            // easy - new course inserted with sortorder 0, the rest is ok
1025            $sql = "UPDATE {course}
1026                       SET sortorder = sortorder + 1
1027                     WHERE category = ?";
1028            $DB->execute($sql, array($cat->id));
1029
1030        } else {
1031            // it needs full resorting
1032            $fixcategories[$cat->id] = $cat;
1033        }
1034        $cacheevents['changesincourse'] = true;
1035    }
1036    unset($gapcategories);
1037
1038    // fix course sortorders in problematic categories only
1039    foreach ($fixcategories as $cat) {
1040        $i = 1;
1041        $courses = $DB->get_records('course', array('category'=>$cat->id), 'sortorder ASC, id DESC', 'id, sortorder');
1042        foreach ($courses as $course) {
1043            if ($course->sortorder != $cat->sortorder + $i) {
1044                $course->sortorder = $cat->sortorder + $i;
1045                $DB->update_record_raw('course', $course, true);
1046                $cacheevents['changesincourse'] = true;
1047            }
1048            $i++;
1049        }
1050    }
1051
1052    // advise all caches that need to be rebuilt
1053    foreach (array_keys($cacheevents) as $event) {
1054        cache_helper::purge_by_event($event);
1055    }
1056}
1057
1058/**
1059 * Internal recursive category verification function, do not use directly!
1060 *
1061 * @todo Document the arguments of this function better
1062 *
1063 * @global object
1064 * @uses MAX_COURSES_IN_CATEGORY
1065 * @uses CONTEXT_COURSECAT
1066 * @param array $children
1067 * @param int $sortorder
1068 * @param string $parent
1069 * @param int $depth
1070 * @param string $path
1071 * @param array $fixcontexts
1072 * @return bool if changes were made
1073 */
1074function _fix_course_cats($children, &$sortorder, $parent, $depth, $path, &$fixcontexts) {
1075    global $DB;
1076
1077    $depth++;
1078    $changesmade = false;
1079
1080    foreach ($children as $cat) {
1081        $sortorder = $sortorder + MAX_COURSES_IN_CATEGORY;
1082        $update = false;
1083        if ($parent != $cat->parent or $depth != $cat->depth or $path.'/'.$cat->id != $cat->path) {
1084            $cat->parent = $parent;
1085            $cat->depth  = $depth;
1086            $cat->path   = $path.'/'.$cat->id;
1087            $update = true;
1088
1089            // make sure context caches are rebuild and dirty contexts marked
1090            $context = context_coursecat::instance($cat->id);
1091            $fixcontexts[$context->id] = $context;
1092        }
1093        if ($cat->sortorder != $sortorder) {
1094            $cat->sortorder = $sortorder;
1095            $update = true;
1096        }
1097        if ($update) {
1098            $DB->update_record('course_categories', $cat, true);
1099            $changesmade = true;
1100        }
1101        if (isset($cat->children)) {
1102            if (_fix_course_cats($cat->children, $sortorder, $cat->id, $cat->depth, $cat->path, $fixcontexts)) {
1103                $changesmade = true;
1104            }
1105        }
1106    }
1107    return $changesmade;
1108}
1109
1110/**
1111 * List of remote courses that a user has access to via MNET.
1112 * Works only on the IDP
1113 *
1114 * @global object
1115 * @global object
1116 * @param int @userid The user id to get remote courses for
1117 * @return array Array of {@link $COURSE} of course objects
1118 */
1119function get_my_remotecourses($userid=0) {
1120    global $DB, $USER;
1121
1122    if (empty($userid)) {
1123        $userid = $USER->id;
1124    }
1125
1126    // we can not use SELECT DISTINCT + text field (summary) because of MS SQL and Oracle, subselect used therefore
1127    $sql = "SELECT c.id, c.remoteid, c.shortname, c.fullname,
1128                   c.hostid, c.summary, c.summaryformat, c.categoryname AS cat_name,
1129                   h.name AS hostname
1130              FROM {mnetservice_enrol_courses} c
1131              JOIN (SELECT DISTINCT hostid, remotecourseid
1132                      FROM {mnetservice_enrol_enrolments}
1133                     WHERE userid = ?
1134                   ) e ON (e.hostid = c.hostid AND e.remotecourseid = c.remoteid)
1135              JOIN {mnet_host} h ON h.id = c.hostid";
1136
1137    return $DB->get_records_sql($sql, array($userid));
1138}
1139
1140/**
1141 * List of remote hosts that a user has access to via MNET.
1142 * Works on the SP
1143 *
1144 * @global object
1145 * @global object
1146 * @return array|bool Array of host objects or false
1147 */
1148function get_my_remotehosts() {
1149    global $CFG, $USER;
1150
1151    if ($USER->mnethostid == $CFG->mnet_localhost_id) {
1152        return false; // Return nothing on the IDP
1153    }
1154    if (!empty($USER->mnet_foreign_host_array) && is_array($USER->mnet_foreign_host_array)) {
1155        return $USER->mnet_foreign_host_array;
1156    }
1157    return false;
1158}
1159
1160/**
1161 * This function creates a default separated/connected scale
1162 *
1163 * This function creates a default separated/connected scale
1164 * so there's something in the database.  The locations of
1165 * strings and files is a bit odd, but this is because we
1166 * need to maintain backward compatibility with many different
1167 * existing language translations and older sites.
1168 *
1169 * @global object
1170 * @return void
1171 */
1172function make_default_scale() {
1173    global $DB;
1174
1175    $defaultscale = new stdClass();
1176    $defaultscale->courseid = 0;
1177    $defaultscale->userid = 0;
1178    $defaultscale->name  = get_string('separateandconnected');
1179    $defaultscale->description = get_string('separateandconnectedinfo');
1180    $defaultscale->scale = get_string('postrating1', 'forum').','.
1181                           get_string('postrating2', 'forum').','.
1182                           get_string('postrating3', 'forum');
1183    $defaultscale->timemodified = time();
1184
1185    $defaultscale->id = $DB->insert_record('scale', $defaultscale);
1186    $DB->execute("UPDATE {forum} SET scale = ?", array($defaultscale->id));
1187}
1188
1189
1190/**
1191 * Returns a menu of all available scales from the site as well as the given course
1192 *
1193 * @global object
1194 * @param int $courseid The id of the course as found in the 'course' table.
1195 * @return array
1196 */
1197function get_scales_menu($courseid=0) {
1198    global $DB;
1199
1200    $sql = "SELECT id, name
1201              FROM {scale}
1202             WHERE courseid = 0 or courseid = ?
1203          ORDER BY courseid ASC, name ASC";
1204    $params = array($courseid);
1205
1206    if ($scales = $DB->get_records_sql_menu($sql, $params)) {
1207        return $scales;
1208    }
1209
1210    make_default_scale();
1211
1212    return $DB->get_records_sql_menu($sql, $params);
1213}
1214
1215/**
1216 * Increment standard revision field.
1217 *
1218 * The revision are based on current time and are incrementing.
1219 * There is a protection for runaway revisions, it may not go further than
1220 * one hour into future.
1221 *
1222 * The field has to be XMLDB_TYPE_INTEGER with size 10.
1223 *
1224 * @param string $table
1225 * @param string $field name of the field containing revision
1226 * @param string $select use empty string when updating all records
1227 * @param array $params optional select parameters
1228 */
1229function increment_revision_number($table, $field, $select, array $params = null) {
1230    global $DB;
1231
1232    $now = time();
1233    $sql = "UPDATE {{$table}}
1234                   SET $field = (CASE
1235                       WHEN $field IS NULL THEN $now
1236                       WHEN $field < $now THEN $now
1237                       WHEN $field > $now + 3600 THEN $now
1238                       ELSE $field + 1 END)";
1239    if ($select) {
1240        $sql = $sql . " WHERE $select";
1241    }
1242    $DB->execute($sql, $params);
1243}
1244
1245
1246/// MODULE FUNCTIONS /////////////////////////////////////////////////
1247
1248/**
1249 * Just gets a raw list of all modules in a course
1250 *
1251 * @global object
1252 * @param int $courseid The id of the course as found in the 'course' table.
1253 * @return array
1254 */
1255function get_course_mods($courseid) {
1256    global $DB;
1257
1258    if (empty($courseid)) {
1259        return false; // avoid warnings
1260    }
1261
1262    return $DB->get_records_sql("SELECT cm.*, m.name as modname
1263                                   FROM {modules} m, {course_modules} cm
1264                                  WHERE cm.course = ? AND cm.module = m.id AND m.visible = 1",
1265                                array($courseid)); // no disabled mods
1266}
1267
1268
1269/**
1270 * Given an id of a course module, finds the coursemodule description
1271 *
1272 * Please note that this function performs 1-2 DB queries. When possible use cached
1273 * course modinfo. For example get_fast_modinfo($courseorid)->get_cm($cmid)
1274 * See also {@link cm_info::get_course_module_record()}
1275 *
1276 * @global object
1277 * @param string $modulename name of module type, eg. resource, assignment,... (optional, slower and less safe if not specified)
1278 * @param int $cmid course module id (id in course_modules table)
1279 * @param int $courseid optional course id for extra validation
1280 * @param bool $sectionnum include relative section number (0,1,2 ...)
1281 * @param int $strictness IGNORE_MISSING means compatible mode, false returned if record not found, debug message if more found;
1282 *                        IGNORE_MULTIPLE means return first, ignore multiple records found(not recommended);
1283 *                        MUST_EXIST means throw exception if no record or multiple records found
1284 * @return stdClass
1285 */
1286function get_coursemodule_from_id($modulename, $cmid, $courseid=0, $sectionnum=false, $strictness=IGNORE_MISSING) {
1287    global $DB;
1288
1289    $params = array('cmid'=>$cmid);
1290
1291    if (!$modulename) {
1292        if (!$modulename = $DB->get_field_sql("SELECT md.name
1293                                                 FROM {modules} md
1294                                                 JOIN {course_modules} cm ON cm.module = md.id
1295                                                WHERE cm.id = :cmid", $params, $strictness)) {
1296            return false;
1297        }
1298    } else {
1299        if (!core_component::is_valid_plugin_name('mod', $modulename)) {
1300            throw new coding_exception('Invalid modulename parameter');
1301        }
1302    }
1303
1304    $params['modulename'] = $modulename;
1305
1306    $courseselect = "";
1307    $sectionfield = "";
1308    $sectionjoin  = "";
1309
1310    if ($courseid) {
1311        $courseselect = "AND cm.course = :courseid";
1312        $params['courseid'] = $courseid;
1313    }
1314
1315    if ($sectionnum) {
1316        $sectionfield = ", cw.section AS sectionnum";
1317        $sectionjoin  = "LEFT JOIN {course_sections} cw ON cw.id = cm.section";
1318    }
1319
1320    $sql = "SELECT cm.*, m.name, md.name AS modname $sectionfield
1321              FROM {course_modules} cm
1322                   JOIN {modules} md ON md.id = cm.module
1323                   JOIN {".$modulename."} m ON m.id = cm.instance
1324                   $sectionjoin
1325             WHERE cm.id = :cmid AND md.name = :modulename
1326                   $courseselect";
1327
1328    return $DB->get_record_sql($sql, $params, $strictness);
1329}
1330
1331/**
1332 * Given an instance number of a module, finds the coursemodule description
1333 *
1334 * Please note that this function performs DB query. When possible use cached course
1335 * modinfo. For example get_fast_modinfo($courseorid)->instances[$modulename][$instance]
1336 * See also {@link cm_info::get_course_module_record()}
1337 *
1338 * @global object
1339 * @param string $modulename name of module type, eg. resource, assignment,...
1340 * @param int $instance module instance number (id in resource, assignment etc. table)
1341 * @param int $courseid optional course id for extra validation
1342 * @param bool $sectionnum include relative section number (0,1,2 ...)
1343 * @param int $strictness IGNORE_MISSING means compatible mode, false returned if record not found, debug message if more found;
1344 *                        IGNORE_MULTIPLE means return first, ignore multiple records found(not recommended);
1345 *                        MUST_EXIST means throw exception if no record or multiple records found
1346 * @return stdClass
1347 */
1348function get_coursemodule_from_instance($modulename, $instance, $courseid=0, $sectionnum=false, $strictness=IGNORE_MISSING) {
1349    global $DB;
1350
1351    if (!core_component::is_valid_plugin_name('mod', $modulename)) {
1352        throw new coding_exception('Invalid modulename parameter');
1353    }
1354
1355    $params = array('instance'=>$instance, 'modulename'=>$modulename);
1356
1357    $courseselect = "";
1358    $sectionfield = "";
1359    $sectionjoin  = "";
1360
1361    if ($courseid) {
1362        $courseselect = "AND cm.course = :courseid";
1363        $params['courseid'] = $courseid;
1364    }
1365
1366    if ($sectionnum) {
1367        $sectionfield = ", cw.section AS sectionnum";
1368        $sectionjoin  = "LEFT JOIN {course_sections} cw ON cw.id = cm.section";
1369    }
1370
1371    $sql = "SELECT cm.*, m.name, md.name AS modname $sectionfield
1372              FROM {course_modules} cm
1373                   JOIN {modules} md ON md.id = cm.module
1374                   JOIN {".$modulename."} m ON m.id = cm.instance
1375                   $sectionjoin
1376             WHERE m.id = :instance AND md.name = :modulename
1377                   $courseselect";
1378
1379    return $DB->get_record_sql($sql, $params, $strictness);
1380}
1381
1382/**
1383 * Returns all course modules of given activity in course
1384 *
1385 * @param string $modulename The module name (forum, quiz, etc.)
1386 * @param int $courseid The course id to get modules for
1387 * @param string $extrafields extra fields starting with m.
1388 * @return array Array of results
1389 */
1390function get_coursemodules_in_course($modulename, $courseid, $extrafields='') {
1391    global $DB;
1392
1393    if (!core_component::is_valid_plugin_name('mod', $modulename)) {
1394        throw new coding_exception('Invalid modulename parameter');
1395    }
1396
1397    if (!empty($extrafields)) {
1398        $extrafields = ", $extrafields";
1399    }
1400    $params = array();
1401    $params['courseid'] = $courseid;
1402    $params['modulename'] = $modulename;
1403
1404
1405    return $DB->get_records_sql("SELECT cm.*, m.name, md.name as modname $extrafields
1406                                   FROM {course_modules} cm, {modules} md, {".$modulename."} m
1407                                  WHERE cm.course = :courseid AND
1408                                        cm.instance = m.id AND
1409                                        md.name = :modulename AND
1410                                        md.id = cm.module", $params);
1411}
1412
1413/**
1414 * Returns an array of all the active instances of a particular module in given courses, sorted in the order they are defined
1415 *
1416 * Returns an array of all the active instances of a particular
1417 * module in given courses, sorted in the order they are defined
1418 * in the course. Returns an empty array on any errors.
1419 *
1420 * The returned objects includle the columns cw.section, cm.visible,
1421 * cm.groupmode, and cm.groupingid, and are indexed by cm.id.
1422 *
1423 * @global object
1424 * @global object
1425 * @param string $modulename The name of the module to get instances for
1426 * @param array $courses an array of course objects.
1427 * @param int $userid
1428 * @param int $includeinvisible
1429 * @return array of module instance objects, including some extra fields from the course_modules
1430 *          and course_sections tables, or an empty array if an error occurred.
1431 */
1432function get_all_instances_in_courses($modulename, $courses, $userid=NULL, $includeinvisible=false) {
1433    global $CFG, $DB;
1434
1435    if (!core_component::is_valid_plugin_name('mod', $modulename)) {
1436        throw new coding_exception('Invalid modulename parameter');
1437    }
1438
1439    $outputarray = array();
1440
1441    if (empty($courses) || !is_array($courses) || count($courses) == 0) {
1442        return $outputarray;
1443    }
1444
1445    list($coursessql, $params) = $DB->get_in_or_equal(array_keys($courses), SQL_PARAMS_NAMED, 'c0');
1446    $params['modulename'] = $modulename;
1447
1448    if (!$rawmods = $DB->get_records_sql("SELECT cm.id AS coursemodule, m.*, cw.section, cm.visible AS visible,
1449                                                 cm.groupmode, cm.groupingid
1450                                            FROM {course_modules} cm, {course_sections} cw, {modules} md,
1451                                                 {".$modulename."} m
1452                                           WHERE cm.course $coursessql AND
1453                                                 cm.instance = m.id AND
1454                                                 cm.section = cw.id AND
1455                                                 md.name = :modulename AND
1456                                                 md.id = cm.module", $params)) {
1457        return $outputarray;
1458    }
1459
1460    foreach ($courses as $course) {
1461        $modinfo = get_fast_modinfo($course, $userid);
1462
1463        if (empty($modinfo->instances[$modulename])) {
1464            continue;
1465        }
1466
1467        foreach ($modinfo->instances[$modulename] as $cm) {
1468            if (!$includeinvisible and !$cm->uservisible) {
1469                continue;
1470            }
1471            if (!isset($rawmods[$cm->id])) {
1472                continue;
1473            }
1474            $instance = $rawmods[$cm->id];
1475            if (!empty($cm->extra)) {
1476                $instance->extra = $cm->extra;
1477            }
1478            $outputarray[] = $instance;
1479        }
1480    }
1481
1482    return $outputarray;
1483}
1484
1485/**
1486 * Returns an array of all the active instances of a particular module in a given course,
1487 * sorted in the order they are defined.
1488 *
1489 * Returns an array of all the active instances of a particular
1490 * module in a given course, sorted in the order they are defined
1491 * in the course. Returns an empty array on any errors.
1492 *
1493 * The returned objects includle the columns cw.section, cm.visible,
1494 * cm.groupmode, and cm.groupingid, and are indexed by cm.id.
1495 *
1496 * Simply calls {@link all_instances_in_courses()} with a single provided course
1497 *
1498 * @param string $modulename The name of the module to get instances for
1499 * @param object $course The course obect.
1500 * @return array of module instance objects, including some extra fields from the course_modules
1501 *          and course_sections tables, or an empty array if an error occurred.
1502 * @param int $userid
1503 * @param int $includeinvisible
1504 */
1505function get_all_instances_in_course($modulename, $course, $userid=NULL, $includeinvisible=false) {
1506    return get_all_instances_in_courses($modulename, array($course->id => $course), $userid, $includeinvisible);
1507}
1508
1509
1510/**
1511 * Determine whether a module instance is visible within a course
1512 *
1513 * Given a valid module object with info about the id and course,
1514 * and the module's type (eg "forum") returns whether the object
1515 * is visible or not according to the 'eye' icon only.
1516 *
1517 * NOTE: This does NOT take into account visibility to a particular user.
1518 * To get visibility access for a specific user, use get_fast_modinfo, get a
1519 * cm_info object from this, and check the ->uservisible property; or use
1520 * the \core_availability\info_module::is_user_visible() static function.
1521 *
1522 * @global object
1523
1524 * @param $moduletype Name of the module eg 'forum'
1525 * @param $module Object which is the instance of the module
1526 * @return bool Success
1527 */
1528function instance_is_visible($moduletype, $module) {
1529    global $DB;
1530
1531    if (!empty($module->id)) {
1532        $params = array('courseid'=>$module->course, 'moduletype'=>$moduletype, 'moduleid'=>$module->id);
1533        if ($records = $DB->get_records_sql("SELECT cm.instance, cm.visible, cm.groupingid, cm.id, cm.course
1534                                               FROM {course_modules} cm, {modules} m
1535                                              WHERE cm.course = :courseid AND
1536                                                    cm.module = m.id AND
1537                                                    m.name = :moduletype AND
1538                                                    cm.instance = :moduleid", $params)) {
1539
1540            foreach ($records as $record) { // there should only be one - use the first one
1541                return $record->visible;
1542            }
1543        }
1544    }
1545    return true;  // visible by default!
1546}
1547
1548
1549/// LOG FUNCTIONS /////////////////////////////////////////////////////
1550
1551/**
1552 * Get instance of log manager.
1553 *
1554 * @param bool $forcereload
1555 * @return \core\log\manager
1556 */
1557function get_log_manager($forcereload = false) {
1558    /** @var \core\log\manager $singleton */
1559    static $singleton = null;
1560
1561    if ($forcereload and isset($singleton)) {
1562        $singleton->dispose();
1563        $singleton = null;
1564    }
1565
1566    if (isset($singleton)) {
1567        return $singleton;
1568    }
1569
1570    $classname = '\tool_log\log\manager';
1571    if (defined('LOG_MANAGER_CLASS')) {
1572        $classname = LOG_MANAGER_CLASS;
1573    }
1574
1575    if (!class_exists($classname)) {
1576        if (!empty($classname)) {
1577            debugging("Cannot find log manager class '$classname'.", DEBUG_DEVELOPER);
1578        }
1579        $classname = '\core\log\dummy_manager';
1580    }
1581
1582    $singleton = new $classname();
1583    return $singleton;
1584}
1585
1586/**
1587 * Add an entry to the config log table.
1588 *
1589 * These are "action" focussed rather than web server hits,
1590 * and provide a way to easily reconstruct changes to Moodle configuration.
1591 *
1592 * @package core
1593 * @category log
1594 * @global moodle_database $DB
1595 * @global stdClass $USER
1596 * @param    string  $name     The name of the configuration change action
1597                               For example 'filter_active' when activating or deactivating a filter
1598 * @param    string  $oldvalue The config setting's previous value
1599 * @param    string  $value    The config setting's new value
1600 * @param    string  $plugin   Plugin name, for example a filter name when changing filter configuration
1601 * @return void
1602 */
1603function add_to_config_log($name, $oldvalue, $value, $plugin) {
1604    global $USER, $DB;
1605
1606    $log = new stdClass();
1607    $log->userid       = during_initial_install() ? 0 :$USER->id; // 0 as user id during install
1608    $log->timemodified = time();
1609    $log->name         = $name;
1610    $log->oldvalue  = $oldvalue;
1611    $log->value     = $value;
1612    $log->plugin    = $plugin;
1613    $DB->insert_record('config_log', $log);
1614}
1615
1616/**
1617 * Store user last access times - called when use enters a course or site
1618 *
1619 * @package core
1620 * @category log
1621 * @global stdClass $USER
1622 * @global stdClass $CFG
1623 * @global moodle_database $DB
1624 * @uses LASTACCESS_UPDATE_SECS
1625 * @uses SITEID
1626 * @param int $courseid  empty courseid means site
1627 * @return void
1628 */
1629function user_accesstime_log($courseid=0) {
1630    global $USER, $CFG, $DB;
1631
1632    if (!isloggedin() or \core\session\manager::is_loggedinas()) {
1633        // no access tracking
1634        return;
1635    }
1636
1637    if (isguestuser()) {
1638        // Do not update guest access times/ips for performance.
1639        return;
1640    }
1641
1642    if (empty($courseid)) {
1643        $courseid = SITEID;
1644    }
1645
1646    $timenow = time();
1647
1648/// Store site lastaccess time for the current user
1649    if ($timenow - $USER->lastaccess > LASTACCESS_UPDATE_SECS) {
1650    /// Update $USER->lastaccess for next checks
1651        $USER->lastaccess = $timenow;
1652
1653        $last = new stdClass();
1654        $last->id         = $USER->id;
1655        $last->lastip     = getremoteaddr();
1656        $last->lastaccess = $timenow;
1657
1658        $DB->update_record_raw('user', $last);
1659    }
1660
1661    if ($courseid == SITEID) {
1662    ///  no user_lastaccess for frontpage
1663        return;
1664    }
1665
1666/// Store course lastaccess times for the current user
1667    if (empty($USER->currentcourseaccess[$courseid]) or ($timenow - $USER->currentcourseaccess[$courseid] > LASTACCESS_UPDATE_SECS)) {
1668
1669        $lastaccess = $DB->get_field('user_lastaccess', 'timeaccess', array('userid'=>$USER->id, 'courseid'=>$courseid));
1670
1671        if ($lastaccess === false) {
1672            // Update course lastaccess for next checks
1673            $USER->currentcourseaccess[$courseid] = $timenow;
1674
1675            $last = new stdClass();
1676            $last->userid     = $USER->id;
1677            $last->courseid   = $courseid;
1678            $last->timeaccess = $timenow;
1679            try {
1680                $DB->insert_record_raw('user_lastaccess', $last, false);
1681            } catch (dml_write_exception $e) {
1682                // During a race condition we can fail to find the data, then it appears.
1683                // If we still can't find it, rethrow the exception.
1684                $lastaccess = $DB->get_field('user_lastaccess', 'timeaccess', array('userid' => $USER->id,
1685                                                                                    'courseid' => $courseid));
1686                if ($lastaccess === false) {
1687                    throw $e;
1688                }
1689                // If we did find it, the race condition was true and another thread has inserted the time for us.
1690                // We can just continue without having to do anything.
1691            }
1692
1693        } else if ($timenow - $lastaccess <  LASTACCESS_UPDATE_SECS) {
1694            // no need to update now, it was updated recently in concurrent login ;-)
1695
1696        } else {
1697            // Update course lastaccess for next checks
1698            $USER->currentcourseaccess[$courseid] = $timenow;
1699
1700            $DB->set_field('user_lastaccess', 'timeaccess', $timenow, array('userid'=>$USER->id, 'courseid'=>$courseid));
1701        }
1702    }
1703}
1704
1705/**
1706 * Select all log records based on SQL criteria
1707 *
1708 * @package core
1709 * @category log
1710 * @global moodle_database $DB
1711 * @param string $select SQL select criteria
1712 * @param array $params named sql type params
1713 * @param string $order SQL order by clause to sort the records returned
1714 * @param string $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set)
1715 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set)
1716 * @param int $totalcount Passed in by reference.
1717 * @return array
1718 */
1719function get_logs($select, array $params=null, $order='l.time DESC', $limitfrom='', $limitnum='', &$totalcount) {
1720    global $DB;
1721
1722    if ($order) {
1723        $order = "ORDER BY $order";
1724    }
1725
1726    $selectsql = "";
1727    $countsql  = "";
1728
1729    if ($select) {
1730        $select = "WHERE $select";
1731    }
1732
1733    $sql = "SELECT COUNT(*)
1734              FROM {log} l
1735           $select";
1736
1737    $totalcount = $DB->count_records_sql($sql, $params);
1738    $allnames = get_all_user_name_fields(true, 'u');
1739    $sql = "SELECT l.*, $allnames, u.picture
1740              FROM {log} l
1741              LEFT JOIN {user} u ON l.userid = u.id
1742           $select
1743            $order";
1744
1745    return $DB->get_records_sql($sql, $params, $limitfrom, $limitnum) ;
1746}
1747
1748
1749/**
1750 * Select all log records for a given course and user
1751 *
1752 * @package core
1753 * @category log
1754 * @global moodle_database $DB
1755 * @uses DAYSECS
1756 * @param int $userid The id of the user as found in the 'user' table.
1757 * @param int $courseid The id of the course as found in the 'course' table.
1758 * @param string $coursestart unix timestamp representing course start date and time.
1759 * @return array
1760 */
1761function get_logs_usercourse($userid, $courseid, $coursestart) {
1762    global $DB;
1763
1764    $params = array();
1765
1766    $courseselect = '';
1767    if ($courseid) {
1768        $courseselect = "AND course = :courseid";
1769        $params['courseid'] = $courseid;
1770    }
1771    $params['userid'] = $userid;
1772    // We have to sanitize this param ourselves here instead of relying on DB.
1773    // Postgres complains if you use name parameter or column alias in GROUP BY.
1774    // See MDL-27696 and 51c3e85 for details.
1775    $coursestart = (int)$coursestart;
1776
1777    return $DB->get_records_sql("SELECT FLOOR((time - $coursestart)/". DAYSECS .") AS day, COUNT(*) AS num
1778                                   FROM {log}
1779                                  WHERE userid = :userid
1780                                        AND time > $coursestart $courseselect
1781                               GROUP BY FLOOR((time - $coursestart)/". DAYSECS .")", $params);
1782}
1783
1784/**
1785 * Select all log records for a given course, user, and day
1786 *
1787 * @package core
1788 * @category log
1789 * @global moodle_database $DB
1790 * @uses HOURSECS
1791 * @param int $userid The id of the user as found in the 'user' table.
1792 * @param int $courseid The id of the course as found in the 'course' table.
1793 * @param string $daystart unix timestamp of the start of the day for which the logs needs to be retrived
1794 * @return array
1795 */
1796function get_logs_userday($userid, $courseid, $daystart) {
1797    global $DB;
1798
1799    $params = array('userid'=>$userid);
1800
1801    $courseselect = '';
1802    if ($courseid) {
1803        $courseselect = "AND course = :courseid";
1804        $params['courseid'] = $courseid;
1805    }
1806    $daystart = (int)$daystart; // note: unfortunately pg complains if you use name parameter or column alias in GROUP BY
1807
1808    return $DB->get_records_sql("SELECT FLOOR((time - $daystart)/". HOURSECS .") AS hour, COUNT(*) AS num
1809                                   FROM {log}
1810                                  WHERE userid = :userid
1811                                        AND time > $daystart $courseselect
1812                               GROUP BY FLOOR((time - $daystart)/". HOURSECS .") ", $params);
1813}
1814
1815/// GENERAL HELPFUL THINGS  ///////////////////////////////////
1816
1817/**
1818 * Dumps a given object's information for debugging purposes
1819 *
1820 * When used in a CLI script, the object's information is written to the standard
1821 * error output stream. When used in a web script, the object is dumped to a
1822 * pre-formatted block with the "notifytiny" CSS class.
1823 *
1824 * @param mixed $object The data to be printed
1825 * @return void output is echo'd
1826 */
1827function print_object($object) {
1828
1829    // we may need a lot of memory here
1830    raise_memory_limit(MEMORY_EXTRA);
1831
1832    if (CLI_SCRIPT) {
1833        fwrite(STDERR, print_r($object, true));
1834        fwrite(STDERR, PHP_EOL);
1835    } else {
1836        echo html_writer::tag('pre', s(print_r($object, true)), array('class' => 'notifytiny'));
1837    }
1838}
1839
1840/**
1841 * This function is the official hook inside XMLDB stuff to delegate its debug to one
1842 * external function.
1843 *
1844 * Any script can avoid calls to this function by defining XMLDB_SKIP_DEBUG_HOOK before
1845 * using XMLDB classes. Obviously, also, if this function doesn't exist, it isn't invoked ;-)
1846 *
1847 * @uses DEBUG_DEVELOPER
1848 * @param string $message string contains the error message
1849 * @param object $object object XMLDB object that fired the debug
1850 */
1851function xmldb_debug($message, $object) {
1852
1853    debugging($message, DEBUG_DEVELOPER);
1854}
1855
1856/**
1857 * @global object
1858 * @uses CONTEXT_COURSECAT
1859 * @return boolean Whether the user can create courses in any category in the system.
1860 */
1861function user_can_create_courses() {
1862    global $DB;
1863    $catsrs = $DB->get_recordset('course_categories');
1864    foreach ($catsrs as $cat) {
1865        if (has_capability('moodle/course:create', context_coursecat::instance($cat->id))) {
1866            $catsrs->close();
1867            return true;
1868        }
1869    }
1870    $catsrs->close();
1871    return false;
1872}
1873
1874/**
1875 * This method can update the values in mulitple database rows for a colum with
1876 * a unique index, without violating that constraint.
1877 *
1878 * Suppose we have a table with a unique index on (otherid, sortorder), and
1879 * for a particular value of otherid, we want to change all the sort orders.
1880 * You have to do this carefully or you will violate the unique index at some time.
1881 * This method takes care of the details for you.
1882 *
1883 * Note that, it is the responsibility of the caller to make sure that the
1884 * requested rename is legal. For example, if you ask for [1 => 2, 2 => 2]
1885 * then you will get a unique key violation error from the database.
1886 *
1887 * @param string $table The database table to modify.
1888 * @param string $field the field that contains the values we are going to change.
1889 * @param array $newvalues oldvalue => newvalue how to change the values.
1890 *      E.g. [1 => 4, 2 => 1, 3 => 3, 4 => 2].
1891 * @param array $otherconditions array fieldname => requestedvalue extra WHERE clause
1892 *      conditions to restrict which rows are affected. E.g. array('otherid' => 123).
1893 * @param int $unusedvalue (defaults to -1) a value that is never used in $ordercol.
1894 */
1895function update_field_with_unique_index($table, $field, array $newvalues,
1896        array $otherconditions, $unusedvalue = -1) {
1897    global $DB;
1898    $safechanges = decompose_update_into_safe_changes($newvalues, $unusedvalue);
1899
1900    $transaction = $DB->start_delegated_transaction();
1901    foreach ($safechanges as $change) {
1902        list($from, $to) = $change;
1903        $otherconditions[$field] = $from;
1904        $DB->set_field($table, $field, $to, $otherconditions);
1905    }
1906    $transaction->allow_commit();
1907}
1908
1909/**
1910 * Helper used by {@link update_field_with_unique_index()}. Given a desired
1911 * set of changes, break them down into single udpates that can be done one at
1912 * a time without breaking any unique index constraints.
1913 *
1914 * Suppose the input is array(1 => 2, 2 => 1) and -1. Then the output will be
1915 * array (array(1, -1), array(2, 1), array(-1, 2)). This function solves this
1916 * problem in the general case, not just for simple swaps. The unit tests give
1917 * more examples.
1918 *
1919 * Note that, it is the responsibility of the caller to make sure that the
1920 * requested rename is legal. For example, if you ask for something impossible
1921 * like array(1 => 2, 2 => 2) then the results are undefined. (You will probably
1922 * get a unique key violation error from the database later.)
1923 *
1924 * @param array $newvalues The desired re-ordering.
1925 *      E.g. array(1 => 4, 2 => 1, 3 => 3, 4 => 2).
1926 * @param int $unusedvalue A value that is not currently used.
1927 * @return array A safe way to perform the re-order. An array of two-element
1928 *      arrays array($from, $to).
1929 *      E.g. array(array(1, -1), array(2, 1), array(4, 2), array(-1, 4)).
1930 */
1931function decompose_update_into_safe_changes(array $newvalues, $unusedvalue) {
1932    $nontrivialmap = array();
1933    foreach ($newvalues as $from => $to) {
1934        if ($from == $unusedvalue || $to == $unusedvalue) {
1935            throw new \coding_exception('Supposedly unused value ' . $unusedvalue . ' is actually used!');
1936        }
1937        if ($from != $to) {
1938            $nontrivialmap[$from] = $to;
1939        }
1940    }
1941
1942    if (empty($nontrivialmap)) {
1943        return array();
1944    }
1945
1946    // First we deal with all renames that are not part of cycles.
1947    // This bit is O(n^2) and it ought to be possible to do better,
1948    // but it does not seem worth the effort.
1949    $safechanges = array();
1950    $nontrivialmapchanged = true;
1951    while ($nontrivialmapchanged) {
1952        $nontrivialmapchanged = false;
1953
1954        foreach ($nontrivialmap as $from => $to) {
1955            if (array_key_exists($to, $nontrivialmap)) {
1956                continue; // Cannot currenly do this rename.
1957            }
1958            // Is safe to do this rename now.
1959            $safechanges[] = array($from, $to);
1960            unset($nontrivialmap[$from]);
1961            $nontrivialmapchanged = true;
1962        }
1963    }
1964
1965    // Are we done?
1966    if (empty($nontrivialmap)) {
1967        return $safechanges;
1968    }
1969
1970    // Now what is left in $nontrivialmap must be a permutation,
1971    // which must be a combination of disjoint cycles. We need to break them.
1972    while (!empty($nontrivialmap)) {
1973        // Extract the first cycle.
1974        reset($nontrivialmap);
1975        $current = $cyclestart = key($nontrivialmap);
1976        $cycle = array();
1977        do {
1978            $cycle[] = $current;
1979            $next = $nontrivialmap[$current];
1980            unset($nontrivialmap[$current]);
1981            $current = $next;
1982        } while ($current != $cyclestart);
1983
1984        // Now convert it to a sequence of safe renames by using a temp.
1985        $safechanges[] = array($cyclestart, $unusedvalue);
1986        $cycle[0] = $unusedvalue;
1987        $to = $cyclestart;
1988        while ($from = array_pop($cycle)) {
1989            $safechanges[] = array($from, $to);
1990            $to = $from;
1991        }
1992    }
1993
1994    return $safechanges;
1995}
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