/lib/moodlelib.php

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<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * moodlelib.php - Moodle main library
 *
 * Main library file of miscellaneous general-purpose Moodle functions.
 * Other main libraries:
 *  - weblib.php      - functions that produce web output
 *  - datalib.php     - functions that access the database
 *
 * @package    core
 * @subpackage lib
 * @copyright  1999 onwards Martin Dougiamas  http://dougiamas.com
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();

// CONSTANTS (Encased in phpdoc proper comments).

// Date and time constants.
/**
 * Time constant - the number of seconds in a year
 */
define('YEARSECS', 31536000);

/**
 * Time constant - the number of seconds in a week
 */
define('WEEKSECS', 604800);

/**
 * Time constant - the number of seconds in a day
 */
define('DAYSECS', 86400);

/**
 * Time constant - the number of seconds in an hour
 */
define('HOURSECS', 3600);

/**
 * Time constant - the number of seconds in a minute
 */
define('MINSECS', 60);

/**
 * Time constant - the number of minutes in a day
 */
define('DAYMINS', 1440);

/**
 * Time constant - the number of minutes in an hour
 */
define('HOURMINS', 60);

// Parameter constants - every call to optional_param(), required_param()
// or clean_param() should have a specified type of parameter.

/**
 * PARAM_ALPHA - contains only english ascii letters a-zA-Z.
 */
define('PARAM_ALPHA',    'alpha');

/**
 * PARAM_ALPHAEXT the same contents as PARAM_ALPHA plus the chars in quotes: "_-" allowed
 * NOTE: originally this allowed "/" too, please use PARAM_SAFEPATH if "/" needed
 */
define('PARAM_ALPHAEXT', 'alphaext');

/**
 * PARAM_ALPHANUM - expected numbers and letters only.
 */
define('PARAM_ALPHANUM', 'alphanum');

/**
 * PARAM_ALPHANUMEXT - expected numbers, letters only and _-.
 */
define('PARAM_ALPHANUMEXT', 'alphanumext');

/**
 * PARAM_AUTH - actually checks to make sure the string is a valid auth plugin
 */
define('PARAM_AUTH',  'auth');

/**
 * PARAM_BASE64 - Base 64 encoded format
 */
define('PARAM_BASE64',   'base64');

/**
 * PARAM_BOOL - converts input into 0 or 1, use for switches in forms and urls.
 */
define('PARAM_BOOL',     'bool');

/**
 * PARAM_CAPABILITY - A capability name, like 'moodle/role:manage'. Actually
 * checked against the list of capabilities in the database.
 */
define('PARAM_CAPABILITY',   'capability');

/**
 * PARAM_CLEANHTML - cleans submitted HTML code. Note that you almost never want
 * to use this. The normal mode of operation is to use PARAM_RAW when receiving
 * the input (required/optional_param or formslib) and then sanitise the HTML
 * using format_text on output. This is for the rare cases when you want to
 * sanitise the HTML on input. This cleaning may also fix xhtml strictness.
 */
define('PARAM_CLEANHTML', 'cleanhtml');

/**
 * PARAM_EMAIL - an email address following the RFC
 */
define('PARAM_EMAIL',   'email');

/**
 * PARAM_FILE - safe file name, all dangerous chars are stripped, protects against XSS, SQL injections and directory traversals
 */
define('PARAM_FILE',   'file');

/**
 * PARAM_FLOAT - a real/floating point number.
 *
 * Note that you should not use PARAM_FLOAT for numbers typed in by the user.
 * It does not work for languages that use , as a decimal separator.
 * Use PARAM_LOCALISEDFLOAT instead.
 */
define('PARAM_FLOAT',  'float');

/**
 * PARAM_LOCALISEDFLOAT - a localised real/floating point number.
 * This is preferred over PARAM_FLOAT for numbers typed in by the user.
 * Cleans localised numbers to computer readable numbers; false for invalid numbers.
 */
define('PARAM_LOCALISEDFLOAT',  'localisedfloat');

/**
 * PARAM_HOST - expected fully qualified domain name (FQDN) or an IPv4 dotted quad (IP address)
 */
define('PARAM_HOST',     'host');

/**
 * PARAM_INT - integers only, use when expecting only numbers.
 */
define('PARAM_INT',      'int');

/**
 * PARAM_LANG - checks to see if the string is a valid installed language in the current site.
 */
define('PARAM_LANG',  'lang');

/**
 * PARAM_LOCALURL - expected properly formatted URL as well as one that refers to the local server itself. (NOT orthogonal to the
 * others! Implies PARAM_URL!)
 */
define('PARAM_LOCALURL', 'localurl');

/**
 * PARAM_NOTAGS - all html tags are stripped from the text. Do not abuse this type.
 */
define('PARAM_NOTAGS',   'notags');

/**
 * PARAM_PATH - safe relative path name, all dangerous chars are stripped, protects against XSS, SQL injections and directory
 * traversals note: the leading slash is not removed, window drive letter is not allowed
 */
define('PARAM_PATH',     'path');

/**
 * PARAM_PEM - Privacy Enhanced Mail format
 */
define('PARAM_PEM',      'pem');

/**
 * PARAM_PERMISSION - A permission, one of CAP_INHERIT, CAP_ALLOW, CAP_PREVENT or CAP_PROHIBIT.
 */
define('PARAM_PERMISSION',   'permission');

/**
 * PARAM_RAW specifies a parameter that is not cleaned/processed in any way except the discarding of the invalid utf-8 characters
 */
define('PARAM_RAW', 'raw');

/**
 * PARAM_RAW_TRIMMED like PARAM_RAW but leading and trailing whitespace is stripped.
 */
define('PARAM_RAW_TRIMMED', 'raw_trimmed');

/**
 * PARAM_SAFEDIR - safe directory name, suitable for include() and require()
 */
define('PARAM_SAFEDIR',  'safedir');

/**
 * PARAM_SAFEPATH - several PARAM_SAFEDIR joined by "/", suitable for include() and require(), plugin paths, etc.
 */
define('PARAM_SAFEPATH',  'safepath');

/**
 * PARAM_SEQUENCE - expects a sequence of numbers like 8 to 1,5,6,4,6,8,9.  Numbers and comma only.
 */
define('PARAM_SEQUENCE',  'sequence');

/**
 * PARAM_TAG - one tag (interests, blogs, etc.) - mostly international characters and space, <> not supported
 */
define('PARAM_TAG',   'tag');

/**
 * PARAM_TAGLIST - list of tags separated by commas (interests, blogs, etc.)
 */
define('PARAM_TAGLIST',   'taglist');

/**
 * PARAM_TEXT - general plain text compatible with multilang filter, no other html tags. Please note '<', or '>' are allowed here.
 */
define('PARAM_TEXT',  'text');

/**
 * PARAM_THEME - Checks to see if the string is a valid theme name in the current site
 */
define('PARAM_THEME',  'theme');

/**
 * PARAM_URL - expected properly formatted URL. Please note that domain part is required, http://localhost/ is not accepted but
 * http://localhost.localdomain/ is ok.
 */
define('PARAM_URL',      'url');

/**
 * PARAM_USERNAME - Clean username to only contains allowed characters. This is to be used ONLY when manually creating user
 * accounts, do NOT use when syncing with external systems!!
 */
define('PARAM_USERNAME',    'username');

/**
 * PARAM_STRINGID - used to check if the given string is valid string identifier for get_string()
 */
define('PARAM_STRINGID',    'stringid');

// DEPRECATED PARAM TYPES OR ALIASES - DO NOT USE FOR NEW CODE.
/**
 * PARAM_CLEAN - obsoleted, please use a more specific type of parameter.
 * It was one of the first types, that is why it is abused so much ;-)
 * @deprecated since 2.0
 */
define('PARAM_CLEAN',    'clean');

/**
 * PARAM_INTEGER - deprecated alias for PARAM_INT
 * @deprecated since 2.0
 */
define('PARAM_INTEGER',  'int');

/**
 * PARAM_NUMBER - deprecated alias of PARAM_FLOAT
 * @deprecated since 2.0
 */
define('PARAM_NUMBER',  'float');

/**
 * PARAM_ACTION - deprecated alias for PARAM_ALPHANUMEXT, use for various actions in forms and urls
 * NOTE: originally alias for PARAM_APLHA
 * @deprecated since 2.0
 */
define('PARAM_ACTION',   'alphanumext');

/**
 * PARAM_FORMAT - deprecated alias for PARAM_ALPHANUMEXT, use for names of plugins, formats, etc.
 * NOTE: originally alias for PARAM_APLHA
 * @deprecated since 2.0
 */
define('PARAM_FORMAT',   'alphanumext');

/**
 * PARAM_MULTILANG - deprecated alias of PARAM_TEXT.
 * @deprecated since 2.0
 */
define('PARAM_MULTILANG',  'text');

/**
 * PARAM_TIMEZONE - expected timezone. Timezone can be int +-(0-13) or float +-(0.5-12.5) or
 * string separated by '/' and can have '-' &/ '_' (eg. America/North_Dakota/New_Salem
 * America/Port-au-Prince)
 */
define('PARAM_TIMEZONE', 'timezone');

/**
 * PARAM_CLEANFILE - deprecated alias of PARAM_FILE; originally was removing regional chars too
 */
define('PARAM_CLEANFILE', 'file');

/**
 * PARAM_COMPONENT is used for full component names (aka frankenstyle) such as 'mod_forum', 'core_rating', 'auth_ldap'.
 * Short legacy subsystem names and module names are accepted too ex: 'forum', 'rating', 'user'.
 * Only lowercase ascii letters, numbers and underscores are allowed, it has to start with a letter.
 * NOTE: numbers and underscores are strongly discouraged in plugin names!
 */
define('PARAM_COMPONENT', 'component');

/**
 * PARAM_AREA is a name of area used when addressing files, comments, ratings, etc.
 * It is usually used together with context id and component.
 * Only lowercase ascii letters, numbers and underscores are allowed, it has to start with a letter.
 */
define('PARAM_AREA', 'area');

/**
 * PARAM_PLUGIN is used for plugin names such as 'forum', 'glossary', 'ldap', 'paypal', 'completionstatus'.
 * Only lowercase ascii letters, numbers and underscores are allowed, it has to start with a letter.
 * NOTE: numbers and underscores are strongly discouraged in plugin names! Underscores are forbidden in module names.
 */
define('PARAM_PLUGIN', 'plugin');


// Web Services.

/**
 * VALUE_REQUIRED - if the parameter is not supplied, there is an error
 */
define('VALUE_REQUIRED', 1);

/**
 * VALUE_OPTIONAL - if the parameter is not supplied, then the param has no value
 */
define('VALUE_OPTIONAL', 2);

/**
 * VALUE_DEFAULT - if the parameter is not supplied, then the default value is used
 */
define('VALUE_DEFAULT', 0);

/**
 * NULL_NOT_ALLOWED - the parameter can not be set to null in the database
 */
define('NULL_NOT_ALLOWED', false);

/**
 * NULL_ALLOWED - the parameter can be set to null in the database
 */
define('NULL_ALLOWED', true);

// Page types.

/**
 * PAGE_COURSE_VIEW is a definition of a page type. For more information on the page class see moodle/lib/pagelib.php.
 */
define('PAGE_COURSE_VIEW', 'course-view');

/** Get remote addr constant */
define('GETREMOTEADDR_SKIP_HTTP_CLIENT_IP', '1');
/** Get remote addr constant */
define('GETREMOTEADDR_SKIP_HTTP_X_FORWARDED_FOR', '2');

// Blog access level constant declaration.
define ('BLOG_USER_LEVEL', 1);
define ('BLOG_GROUP_LEVEL', 2);
define ('BLOG_COURSE_LEVEL', 3);
define ('BLOG_SITE_LEVEL', 4);
define ('BLOG_GLOBAL_LEVEL', 5);


// Tag constants.
/**
 * To prevent problems with multibytes strings,Flag updating in nav not working on the review page. this should not exceed the
 * length of "varchar(255) / 3 (bytes / utf-8 character) = 85".
 * TODO: this is not correct, varchar(255) are 255 unicode chars ;-)
 *
 * @todo define(TAG_MAX_LENGTH) this is not correct, varchar(255) are 255 unicode chars ;-)
 */
define('TAG_MAX_LENGTH', 50);

// Password policy constants.
define ('PASSWORD_LOWER', 'abcdefghijklmnopqrstuvwxyz');
define ('PASSWORD_UPPER', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ');
define ('PASSWORD_DIGITS', '0123456789');
define ('PASSWORD_NONALPHANUM', '.,;:!?_-+/*@#&$');

// Feature constants.
// Used for plugin_supports() to report features that are, or are not, supported by a module.

/** True if module can provide a grade */
define('FEATURE_GRADE_HAS_GRADE', 'grade_has_grade');
/** True if module supports outcomes */
define('FEATURE_GRADE_OUTCOMES', 'outcomes');
/** True if module supports advanced grading methods */
define('FEATURE_ADVANCED_GRADING', 'grade_advanced_grading');
/** True if module controls the grade visibility over the gradebook */
define('FEATURE_CONTROLS_GRADE_VISIBILITY', 'controlsgradevisbility');
/** True if module supports plagiarism plugins */
define('FEATURE_PLAGIARISM', 'plagiarism');

/** True if module has code to track whether somebody viewed it */
define('FEATURE_COMPLETION_TRACKS_VIEWS', 'completion_tracks_views');
/** True if module has custom completion rules */
define('FEATURE_COMPLETION_HAS_RULES', 'completion_has_rules');

/** True if module has no 'view' page (like label) */
define('FEATURE_NO_VIEW_LINK', 'viewlink');
/** True (which is default) if the module wants support for setting the ID number for grade calculation purposes. */
define('FEATURE_IDNUMBER', 'idnumber');
/** True if module supports groups */
define('FEATURE_GROUPS', 'groups');
/** True if module supports groupings */
define('FEATURE_GROUPINGS', 'groupings');
/**
 * True if module supports groupmembersonly (which no longer exists)
 * @deprecated Since Moodle 2.8
 */
define('FEATURE_GROUPMEMBERSONLY', 'groupmembersonly');

/** Type of module */
define('FEATURE_MOD_ARCHETYPE', 'mod_archetype');
/** True if module supports intro editor */
define('FEATURE_MOD_INTRO', 'mod_intro');
/** True if module has default completion */
define('FEATURE_MODEDIT_DEFAULT_COMPLETION', 'modedit_default_completion');

define('FEATURE_COMMENT', 'comment');

define('FEATURE_RATE', 'rate');
/** True if module supports backup/restore of moodle2 format */
define('FEATURE_BACKUP_MOODLE2', 'backup_moodle2');

/** True if module can show description on course main page */
define('FEATURE_SHOW_DESCRIPTION', 'showdescription');

/** True if module uses the question bank */
define('FEATURE_USES_QUESTIONS', 'usesquestions');

/**
 * Maximum filename char size
 */
define('MAX_FILENAME_SIZE', 100);

/** Unspecified module archetype */
define('MOD_ARCHETYPE_OTHER', 0);
/** Resource-like type module */
define('MOD_ARCHETYPE_RESOURCE', 1);
/** Assignment module archetype */
define('MOD_ARCHETYPE_ASSIGNMENT', 2);
/** System (not user-addable) module archetype */
define('MOD_ARCHETYPE_SYSTEM', 3);

/**
 * Security token used for allowing access
 * from external application such as web services.
 * Scripts do not use any session, performance is relatively
 * low because we need to load access info in each request.
 * Scripts are executed in parallel.
 */
define('EXTERNAL_TOKEN_PERMANENT', 0);

/**
 * Security token used for allowing access
 * of embedded applications, the code is executed in the
 * active user session. Token is invalidated after user logs out.
 * Scripts are executed serially - normal session locking is used.
 */
define('EXTERNAL_TOKEN_EMBEDDED', 1);

/**
 * The home page should be the site home
 */
define('HOMEPAGE_SITE', 0);
/**
 * The home page should be the users my page
 */
define('HOMEPAGE_MY', 1);
/**
 * The home page can be chosen by the user
 */
define('HOMEPAGE_USER', 2);

/**
 * URL of the Moodle sites registration portal.
 */
defined('HUB_MOODLEORGHUBURL') || define('HUB_MOODLEORGHUBURL', 'https://stats.moodle.org');

/**
 * Moodle mobile app service name
 */
define('MOODLE_OFFICIAL_MOBILE_SERVICE', 'moodle_mobile_app');

/**
 * Indicates the user has the capabilities required to ignore activity and course file size restrictions
 */
define('USER_CAN_IGNORE_FILE_SIZE_LIMITS', -1);

/**
 * Course display settings: display all sections on one page.
 */
define('COURSE_DISPLAY_SINGLEPAGE', 0);
/**
 * Course display settings: split pages into a page per section.
 */
define('COURSE_DISPLAY_MULTIPAGE', 1);

/**
 * Authentication constant: String used in password field when password is not stored.
 */
define('AUTH_PASSWORD_NOT_CACHED', 'not cached');

/**
 * Email from header to never include via information.
 */
define('EMAIL_VIA_NEVER', 0);

/**
 * Email from header to always include via information.
 */
define('EMAIL_VIA_ALWAYS', 1);

/**
 * Email from header to only include via information if the address is no-reply.
 */
define('EMAIL_VIA_NO_REPLY_ONLY', 2);

// PARAMETER HANDLING.

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET.  If the parameter doesn't exist then an error is
 * thrown because we require this variable.
 *
 * This function should be used to initialise all required values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $id = required_param('id', PARAM_INT);
 *
 * Please note the $type parameter is now required and the value can not be array.
 *
 * @param string $parname the name of the page parameter we want
 * @param string $type expected type of parameter
 * @return mixed
 * @throws coding_exception
 */
function required_param($parname, $type) {
    if (func_num_args() != 2 or empty($parname) or empty($type)) {
        throw new coding_exception('required_param() requires $parname and $type to be specified (parameter: '.$parname.')');
    }
    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        print_error('missingparam', '', '', $parname);
    }

    if (is_array($param)) {
        debugging('Invalid array parameter detected in required_param(): '.$parname);
        // TODO: switch to fatal error in Moodle 2.3.
        return required_param_array($parname, $type);
    }

    return clean_param($param, $type);
}

/**
 * Returns a particular array value for the named variable, taken from
 * POST or GET.  If the parameter doesn't exist then an error is
 * thrown because we require this variable.
 *
 * This function should be used to initialise all required values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $ids = required_param_array('ids', PARAM_INT);
 *
 *  Note: arrays of arrays are not supported, only alphanumeric keys with _ and - are supported
 *
 * @param string $parname the name of the page parameter we want
 * @param string $type expected type of parameter
 * @return array
 * @throws coding_exception
 */
function required_param_array($parname, $type) {
    if (func_num_args() != 2 or empty($parname) or empty($type)) {
        throw new coding_exception('required_param_array() requires $parname and $type to be specified (parameter: '.$parname.')');
    }
    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        print_error('missingparam', '', '', $parname);
    }
    if (!is_array($param)) {
        print_error('missingparam', '', '', $parname);
    }

    $result = array();
    foreach ($param as $key => $value) {
        if (!preg_match('/^[a-z0-9_-]+$/i', $key)) {
            debugging('Invalid key name in required_param_array() detected: '.$key.', parameter: '.$parname);
            continue;
        }
        $result[$key] = clean_param($value, $type);
    }

    return $result;
}

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET, otherwise returning a given default.
 *
 * This function should be used to initialise all optional values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $name = optional_param('name', 'Fred', PARAM_TEXT);
 *
 * Please note the $type parameter is now required and the value can not be array.
 *
 * @param string $parname the name of the page parameter we want
 * @param mixed  $default the default value to return if nothing is found
 * @param string $type expected type of parameter
 * @return mixed
 * @throws coding_exception
 */
function optional_param($parname, $default, $type) {
    if (func_num_args() != 3 or empty($parname) or empty($type)) {
        throw new coding_exception('optional_param requires $parname, $default + $type to be specified (parameter: '.$parname.')');
    }

    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        return $default;
    }

    if (is_array($param)) {
        debugging('Invalid array parameter detected in required_param(): '.$parname);
        // TODO: switch to $default in Moodle 2.3.
        return optional_param_array($parname, $default, $type);
    }

    return clean_param($param, $type);
}

/**
 * Returns a particular array value for the named variable, taken from
 * POST or GET, otherwise returning a given default.
 *
 * This function should be used to initialise all optional values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $ids = optional_param('id', array(), PARAM_INT);
 *
 * Note: arrays of arrays are not supported, only alphanumeric keys with _ and - are supported
 *
 * @param string $parname the name of the page parameter we want
 * @param mixed $default the default value to return if nothing is found
 * @param string $type expected type of parameter
 * @return array
 * @throws coding_exception
 */
function optional_param_array($parname, $default, $type) {
    if (func_num_args() != 3 or empty($parname) or empty($type)) {
        throw new coding_exception('optional_param_array requires $parname, $default + $type to be specified (parameter: '.$parname.')');
    }

    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        return $default;
    }
    if (!is_array($param)) {
        debugging('optional_param_array() expects array parameters only: '.$parname);
        return $default;
    }

    $result = array();
    foreach ($param as $key => $value) {
        if (!preg_match('/^[a-z0-9_-]+$/i', $key)) {
            debugging('Invalid key name in optional_param_array() detected: '.$key.', parameter: '.$parname);
            continue;
        }
        $result[$key] = clean_param($value, $type);
    }

    return $result;
}

/**
 * Strict validation of parameter values, the values are only converted
 * to requested PHP type. Internally it is using clean_param, the values
 * before and after cleaning must be equal - otherwise
 * an invalid_parameter_exception is thrown.
 * Objects and classes are not accepted.
 *
 * @param mixed $param
 * @param string $type PARAM_ constant
 * @param bool $allownull are nulls valid value?
 * @param string $debuginfo optional debug information
 * @return mixed the $param value converted to PHP type
 * @throws invalid_parameter_exception if $param is not of given type
 */
function validate_param($param, $type, $allownull=NULL_NOT_ALLOWED, $debuginfo='') {
    if (is_null($param)) {
        if ($allownull == NULL_ALLOWED) {
            return null;
        } else {
            throw new invalid_parameter_exception($debuginfo);
        }
    }
    if (is_array($param) or is_object($param)) {
        throw new invalid_parameter_exception($debuginfo);
    }

    $cleaned = clean_param($param, $type);

    if ($type == PARAM_FLOAT) {
        // Do not detect precision loss here.
        if (is_float($param) or is_int($param)) {
            // These always fit.
        } else if (!is_numeric($param) or !preg_match('/^[\+-]?[0-9]*\.?[0-9]*(e[-+]?[0-9]+)?$/i', (string)$param)) {
            throw new invalid_parameter_exception($debuginfo);
        }
    } else if ((string)$param !== (string)$cleaned) {
        // Conversion to string is usually lossless.
        throw new invalid_parameter_exception($debuginfo);
    }

    return $cleaned;
}

/**
 * Makes sure array contains only the allowed types, this function does not validate array key names!
 *
 * <code>
 * $options = clean_param($options, PARAM_INT);
 * </code>
 *
 * @param array $param the variable array we are cleaning
 * @param string $type expected format of param after cleaning.
 * @param bool $recursive clean recursive arrays
 * @return array
 * @throws coding_exception
 */
function clean_param_array(array $param = null, $type, $recursive = false) {
    // Convert null to empty array.
    $param = (array)$param;
    foreach ($param as $key => $value) {
        if (is_array($value)) {
            if ($recursive) {
                $param[$key] = clean_param_array($value, $type, true);
            } else {
                throw new coding_exception('clean_param_array can not process multidimensional arrays when $recursive is false.');
            }
        } else {
            $param[$key] = clean_param($value, $type);
        }
    }
    return $param;
}

/**
 * Used by {@link optional_param()} and {@link required_param()} to
 * clean the variables and/or cast to specific types, based on
 * an options field.
 * <code>
 * $course->format = clean_param($course->format, PARAM_ALPHA);
 * $selectedgradeitem = clean_param($selectedgradeitem, PARAM_INT);
 * </code>
 *
 * @param mixed $param the variable we are cleaning
 * @param string $type expected format of param after cleaning.
 * @return mixed
 * @throws coding_exception
 */
function clean_param($param, $type) {
    global $CFG;

    if (is_array($param)) {
        throw new coding_exception('clean_param() can not process arrays, please use clean_param_array() instead.');
    } else if (is_object($param)) {
        if (method_exists($param, '__toString')) {
            $param = $param->__toString();
        } else {
            throw new coding_exception('clean_param() can not process objects, please use clean_param_array() instead.');
        }
    }

    switch ($type) {
        case PARAM_RAW:
            // No cleaning at all.
            $param = fix_utf8($param);
            return $param;

        case PARAM_RAW_TRIMMED:
            // No cleaning, but strip leading and trailing whitespace.
            $param = fix_utf8($param);
            return trim($param);

        case PARAM_CLEAN:
            // General HTML cleaning, try to use more specific type if possible this is deprecated!
            // Please use more specific type instead.
            if (is_numeric($param)) {
                return $param;
            }
            $param = fix_utf8($param);
            // Sweep for scripts, etc.
            return clean_text($param);

        case PARAM_CLEANHTML:
            // Clean html fragment.
            $param = fix_utf8($param);
            // Sweep for scripts, etc.
            $param = clean_text($param, FORMAT_HTML);
            return trim($param);

        case PARAM_INT:
            // Convert to integer.
            return (int)$param;

        case PARAM_FLOAT:
            // Convert to float.
            return (float)$param;

        case PARAM_LOCALISEDFLOAT:
            // Convert to float.
            return unformat_float($param, true);

        case PARAM_ALPHA:
            // Remove everything not `a-z`.
            return preg_replace('/[^a-zA-Z]/i', '', $param);

        case PARAM_ALPHAEXT:
            // Remove everything not `a-zA-Z_-` (originally allowed "/" too).
            return preg_replace('/[^a-zA-Z_-]/i', '', $param);

        case PARAM_ALPHANUM:
            // Remove everything not `a-zA-Z0-9`.
            return preg_replace('/[^A-Za-z0-9]/i', '', $param);

        case PARAM_ALPHANUMEXT:
            // Remove everything not `a-zA-Z0-9_-`.
            return preg_replace('/[^A-Za-z0-9_-]/i', '', $param);

        case PARAM_SEQUENCE:
            // Remove everything not `0-9,`.
            return preg_replace('/[^0-9,]/i', '', $param);

        case PARAM_BOOL:
            // Convert to 1 or 0.
            $tempstr = strtolower($param);
            if ($tempstr === 'on' or $tempstr === 'yes' or $tempstr === 'true') {
                $param = 1;
            } else if ($tempstr === 'off' or $tempstr === 'no'  or $tempstr === 'false') {
                $param = 0;
            } else {
                $param = empty($param) ? 0 : 1;
            }
            return $param;

        case PARAM_NOTAGS:
            // Strip all tags.
            $param = fix_utf8($param);
            return strip_tags($param);

        case PARAM_TEXT:
            // Leave only tags needed for multilang.
            $param = fix_utf8($param);
            // If the multilang syntax is not correct we strip all tags because it would break xhtml strict which is required
            // for accessibility standards please note this cleaning does not strip unbalanced '>' for BC compatibility reasons.
            do {
                if (strpos($param, '</lang>') !== false) {
                    // Old and future mutilang syntax.
                    $param = strip_tags($param, '<lang>');
                    if (!preg_match_all('/<.*>/suU', $param, $matches)) {
                        break;
                    }
                    $open = false;
                    foreach ($matches[0] as $match) {
                        if ($match === '</lang>') {
                            if ($open) {
                                $open = false;
                                continue;
                            } else {
                                break 2;
                            }
                        }
                        if (!preg_match('/^<lang lang="[a-zA-Z0-9_-]+"\s*>$/u', $match)) {
                            break 2;
                        } else {
                            $open = true;
                        }
                    }
                    if ($open) {
                        break;
                    }
                    return $param;

                } else if (strpos($param, '</span>') !== false) {
                    // Current problematic multilang syntax.
                    $param = strip_tags($param, '<span>');
                    if (!preg_match_all('/<.*>/suU', $param, $matches)) {
                        break;
                    }
                    $open = false;
                    foreach ($matches[0] as $match) {
                        if ($match === '</span>') {
                            if ($open) {
                                $open = false;
                                continue;
                            } else {
                                break 2;
                            }
                        }
                        if (!preg_match('/^<span(\s+lang="[a-zA-Z0-9_-]+"|\s+class="multilang"){2}\s*>$/u', $match)) {
                            break 2;
                        } else {
                            $open = true;
                        }
                    }
                    if ($open) {
                        break;
                    }
                    return $param;
                }
            } while (false);
            // Easy, just strip all tags, if we ever want to fix orphaned '&' we have to do that in format_string().
            return strip_tags($param);

        case PARAM_COMPONENT:
            // We do not want any guessing here, either the name is correct or not
            // please note only normalised component names are accepted.
            if (!preg_match('/^[a-z][a-z0-9]*(_[a-z][a-z0-9_]*)?[a-z0-9]+$/', $param)) {
                return '';
            }
            if (strpos($param, '__') !== false) {
                return '';
            }
            if (strpos($param, 'mod_') === 0) {
                // Module names must not contain underscores because we need to differentiate them from invalid plugin types.
                if (substr_count($param, '_') != 1) {
                    return '';
                }
            }
            return $param;

        case PARAM_PLUGIN:
        case PARAM_AREA:
            // We do not want any guessing here, either the name is correct or not.
            if (!is_valid_plugin_name($param)) {
                return '';
            }
            return $param;

        case PARAM_SAFEDIR:
            // Remove everything not a-zA-Z0-9_- .
            return preg_replace('/[^a-zA-Z0-9_-]/i', '', $param);

        case PARAM_SAFEPATH:
            // Remove everything not a-zA-Z0-9/_- .
            return preg_replace('/[^a-zA-Z0-9\/_-]/i', '', $param);

        case PARAM_FILE:
            // Strip all suspicious characters from filename.
            $param = fix_utf8($param);
            $param = preg_replace('~[[:cntrl:]]|[&<>"`\|\':\\\\/]~u', '', $param);
            if ($param === '.' || $param === '..') {
                $param = '';
            }
            return $param;

        case PARAM_PATH:
            // Strip all suspicious characters from file path.
            $param = fix_utf8($param);
            $param = str_replace('\\', '/', $param);

            // Explode the path and clean each element using the PARAM_FILE rules.
            $breadcrumb = explode('/', $param);
            foreach ($breadcrumb as $key => $crumb) {
                if ($crumb === '.' && $key === 0) {
                    // Special condition to allow for relative current path such as ./currentdirfile.txt.
                } else {
                    $crumb = clean_param($crumb, PARAM_FILE);
                }
                $breadcrumb[$key] = $crumb;
            }
            $param = implode('/', $breadcrumb);

            // Remove multiple current path (./././) and multiple slashes (///).
            $param = preg_replace('~//+~', '/', $param);
            $param = preg_replace('~/(\./)+~', '/', $param);
            return $param;

        case PARAM_HOST:
            // Allow FQDN or IPv4 dotted quad.
            $param = preg_replace('/[^\.\d\w-]/', '', $param );
            // Match ipv4 dotted quad.
            if (preg_match('/(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/', $param, $match)) {
                // Confirm values are ok.
                if ( $match[0] > 255
                     || $match[1] > 255
                     || $match[3] > 255
                     || $match[4] > 255 ) {
                    // Hmmm, what kind of dotted quad is this?
                    $param = '';
                }
            } else if ( preg_match('/^[\w\d\.-]+$/', $param) // Dots, hyphens, numbers.
                       && !preg_match('/^[\.-]/',  $param) // No leading dots/hyphens.
                       && !preg_match('/[\.-]$/',  $param) // No trailing dots/hyphens.
                       ) {
                // All is ok - $param is respected.
            } else {
                // All is not ok...
                $param='';
            }
            return $param;

        case PARAM_URL:
            // Allow safe urls.
            $param = fix_utf8($param);
            include_once($CFG->dirroot . '/lib/validateurlsyntax.php');
            if (!empty($param) && validateUrlSyntax($param, 's?H?S?F?E-u-P-a?I?p?f?q?r?')) {
                // All is ok, param is respected.
            } else {
                // Not really ok.
                $param ='';
            }
            return $param;

        case PARAM_LOCALURL:
            // Allow http absolute, root relative and relative URLs within wwwroot.
            $param = clean_param($param, PARAM_URL);
            if (!empty($param)) {

                if ($param === $CFG->wwwroot) {
                    // Exact match;
                } else if (preg_match(':^/:', $param)) {
                    // Root-relative, ok!
                } else if (preg_match('/^' . preg_quote($CFG->wwwroot . '/', '/') . '/i', $param)) {
                    // Absolute, and matches our wwwroot.
                } else {
                    // Relative - let's make sure there are no tricks.
                    if (validateUrlSyntax('/' . $param, 's-u-P-a-p-f+q?r?')) {
                        // Looks ok.
                    } else {
                        $param = '';
                    }
                }
            }
            return $param;

        case PARAM_PEM:
            $param = trim($param);
            // PEM formatted strings may contain letters/numbers and the symbols:
            //   forward slash: /
            //   plus sign:     +
            //   equal sign:    =
            //   , surrounded by BEGIN and END CERTIFICATE prefix and suffixes.
            if (preg_match('/^-----BEGIN CERTIFICATE-----([\s\w\/\+=]+)-----END CERTIFICATE-----$/', trim($param), $matches)) {
                list($wholething, $body) = $matches;
                unset($wholething, $matches);
                $b64 = clean_param($body, PARAM_BASE64);
                if (!empty($b64)) {
                    return "-----BEGIN CERTIFICATE-----\n$b64\n-----END CERTIFICATE-----\n";
                } else {
                    return '';
                }
            }
            return '';

        case PARAM_BASE64:
            if (!empty($param)) {
                // PEM formatted strings may contain letters/numbers and the symbols
                //   forward slash: /
                //   plus sign:     +
                //   equal sign:    =.
                if (0 >= preg_match('/^([\s\w\/\+=]+)$/', trim($param))) {
                    return '';
                }
                $lines = preg_split('/[\s]+/', $param, -1, PREG_SPLIT_NO_EMPTY);
                // Each line of base64 encoded data must be 64 characters in length, except for the last line which may be less
                // than (or equal to) 64 characters long.
                for ($i=0, $j=count($lines); $i < $j; $i++) {
                    if ($i + 1 == $j) {
                        if (64 < strlen($lines[$i])) {
                            return '';
                        }
                        continue;
                    }

                    if (64 != strlen($lines[$i])) {
                        return '';
                    }
                }
                return implode("\n", $lines);
            } else {
                return '';
            }

        case PARAM_TAG:
            $param = fix_utf8($param);
            // Please note it is not safe to use the tag name directly anywhere,
            // it must be processed with s(), urlencode() before embedding anywhere.
            // Remove some nasties.
            $param = preg_replace('~[[:cntrl:]]|[<>`]~u', '', $param);
            // Convert many whitespace chars into one.
            $param = preg_replace('/\s+/u', ' ', $param);
            $param = core_text::substr(trim($param), 0, TAG_MAX_LENGTH);
            return $param;

        case PARAM_TAGLIST:
            $param = fix_utf8($param);
            $tags = explode(',', $param);
            $result = array();
            foreach ($tags as $tag) {
                $res = clean_param($tag, PARAM_TAG);
                if ($res !== '') {
                    $result[] = $res;
                }
            }
            if ($result) {
                return implode(',', $result);
            } else {
                return '';
            }

        case PARAM_CAPABILITY:
            if (get_capability_info($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_PERMISSION:
            $param = (int)$param;
            if (in_array($param, array(CAP_INHERIT, CAP_ALLOW, CAP_PREVENT, CAP_PROHIBIT))) {
                return $param;
            } else {
                return CAP_INHERIT;
            }

        case PARAM_AUTH:
            $param = clean_param($param, PARAM_PLUGIN);
            if (empty($param)) {
                return '';
            } else if (exists_auth_plugin($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_LANG:
            $param = clean_param($param, PARAM_SAFEDIR);
            if (get_string_manager()->translation_exists($param)) {
                return $param;
            } else {
                // Specified language is not installed or param malformed.
                return '';
            }

        case PARAM_THEME:
            $param = clean_param($param, PARAM_PLUGIN);
            if (empty($param)) {
                return '';
            } else if (file_exists("$CFG->dirroot/theme/$param/config.php")) {
                return $param;
            } else if (!empty($CFG->themedir) and file_exists("$CFG->themedir/$param/config.php")) {
                return $param;
            } else {
                // Specified theme is not installed.
                return '';
            }

        case PARAM_USERNAME:
            $param = fix_utf8($param);
            $param = trim($param);
            // Convert uppercase to lowercase MDL-16919.
            $param = core_text::strtolower($param);
            if (empty($CFG->extendedusernamechars)) {
                $param = str_replace(" " , "", $param);
                // Regular expression, eliminate all chars EXCEPT:
                // alphanum, dash (-), underscore (_), at sign (@) and period (.) characters.
                $param = preg_replace('/[^-\.@_a-z0-9]/', '', $param);
            }
            return $param;

        case PARAM_EMAIL:
            $param = fix_utf8($param);
            if (validate_email($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_STRINGID:
            if (preg_match('|^[a-zA-Z][a-zA-Z0-9\.:/_-]*$|', $param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_TIMEZONE:
            // Can be int, float(with .5 or .0) or string seperated by '/' and can have '-_'.
            $param = fix_utf8($param);
            $timezonepattern = '/^(([+-]?(0?[0-9](\.[5|0])?|1[0-3](\.0)?|1[0-2]\.5))|(99)|[[:alnum:]]+(\/?[[:alpha:]_-])+)$/';
            if (preg_match($timezonepattern, $param)) {
                return $param;
            } else {
                return '';
            }

        default:
            // Doh! throw error, switched parameters in optional_param or another serious problem.
            print_error("unknownparamtype", '', '', $type);
    }
}

/**
 * Whether the PARAM_* type is compatible in RTL.
 *
 * Being compatible with RTL means that the data they contain can flow
 * from right-to-left or left-to-right without compromising the user experience.
 *
 * Take URLs for example, they are not RTL compatible as they should always
 * flow from the left to the right. This also applies to numbers, email addresses,
 * configuration snippets, base64 strings, etc...
 *
 * This function tries to best guess which parameters can contain localised strings.
 *
 * @param string $paramtype Constant PARAM_*.
 * @return bool
 */
function is_rtl_compatible($paramtype) {
    return $paramtype == PARAM_TEXT || $paramtype == PARAM_NOTAGS;
}

/**
 * Makes sure the data is using valid utf8, invalid characters are discarded.
 *
 * Note: this function is not intended for full objects with methods and private properties.
 *
 * @param mixed $value
 * @return mixed with proper utf-8 encoding
 */
function fix_utf8($value) {
    if (is_null($value) or $value === '') {
        return $value;

    } else if (is_string($value)) {
        if ((string)(int)$value === $value) {
            // Shortcut.
            return $value;
        }
        // No null bytes expected in our data, so let's remove it.
        $value = str_replace("\0", '', $value);

        // Note: this duplicates min_fix_utf8() intentionally.
        static $buggyiconv = null;
        if ($buggyiconv === null) {
            $buggyiconv = (!function_exists('iconv') or @iconv('UTF-8', 'UTF-8//IGNORE', '100'.chr(130).'€') !== '100€');
        }

        if ($buggyiconv) {
            if (function_exists('mb_convert_encoding')) {
                $subst = mb_substitute_character();
                mb_substitute_character('');
                $result = mb_convert_encoding($value, 'utf-8', 'utf-8');
                mb_substitute_character($subst);

            } else {
                // Warn admins on admin/index.php page.
                $result = $value;
            }

        } else {
            $result = @iconv('UTF-8', 'UTF-8//IGNORE', $value);
        }

        return $result;

    } else if (is_array($value)) {
        foreach ($value as $k => $v) {
            $value[$k] = fix_utf8($v);
        }
        return $value;

    } else if (is_object($value)) {
        // Do not modify original.
        $value = clone($value);
        foreach ($value as $k => $v) {
            $value->$k = fix_utf8($v);
        }
        return $value;

    } else {
        // This is some other type, no utf-8 here.
        return $value;
    }
}

/**
 * Return true if given value is integer or string with integer value
 *
 * @param mixed $value String or Int
 * @return bool true if number, false if not
 */
function is_number($value) {
    if (is_int($value)) {
        return true;
    } else if (is_string($value)) {
        return ((string)(int)$value) === $value;
    } else {
        return false;
    }
}

/**
 * Returns host part from url.
 *
 * @param string $url full url
 * @return string host, null if not found
 */
function get_host_from_url($url) {
    preg_match('|^[a-z]+://([a-zA-Z0-9-.]+)|i', $url, $matches);
    if ($matches) {
        return $matches[1];
    }
    return null;
}

/**
 * Tests whether anything was returned by text editor
 *
 * This function is useful for testing whether something you got back from
 * the HTML editor actually contains anything. Sometimes the HTML editor
 * appear to be empty, but actually you get back a <br> tag or something.
 *
 * @param string $string a string containing HTML.
 * @return boolean does the string contain any actual content - that is text,
 * images, objects, etc.
 */
function html_is_blank($string) {
    return trim(strip_tags($string, '<img><object><applet><input><select><textarea><hr>')) == '';
}

/**
 * Set a key in global configuration
 *
 * Set a key/value pair in both this session's {@link $CFG} global variable
 * and in the 'config' database table for future sessions.
 *
 * Can also be used to update keys for plugin-scoped configs in config_plugin table.
 * In that case it doesn't affect $CFG.
 *
 * A NULL value will delete the entry.
 *
 * NOTE: this function is called from lib/db/upgrade.php
 *
 * @param string $name the key to set
 * @param string $value the value to set (without magic quotes)
 * @param string $plugin (optional) the plugin scope, default null
 * @return bool true or exception
 */
function set_config($name, $value, $plugin=null) {
    global $CFG, $DB;

    if (empty($plugin)) {
        if (!array_key_exists($name, $CFG->config_php_settings)) {
            // So it's defined for this invocation at least.
            if (is_null($value)) {
                unset($CFG->$name);
            } else {
                // Settings from db are always strings.
                $CFG->$name = (string)$value;
            }
        }

        if ($DB->get_field('config', 'name', array('name' => $name))) {
            if ($value === null) {
                $DB->delete_records('config', array('name' => $name));
            } else {
                $DB->set_field('config', 'value', $value, array('name' => $name));
            }
        } else {
            if ($value !== null) {
                $config = new stdClass();
                $config->name  = $name;
                $config->value = $value;
                $DB->insert_record('config', $config, false);
            }
            // When setting config during a Behat test (in the CLI script, not in the web browser
            // requests), remember which ones are set so that we can clear them later.
            if (defined('BEHAT_TEST')) {
                if (!property_exists($CFG, 'behat_cli_added_config')) {
                    $CFG->behat_cli_added_config = [];
                }
                $CFG->behat_cli_added_config[$name] = true;
            }
        }
        if ($name === 'siteidentifier') {
            cache_helper::update_site_identifier($value);
        }
        cache_helper::invalidate_by_definition('core', 'config', array(), 'core');
    } else {
        // Plugin scope.
        if ($id = $DB->get_field('config_plugins', 'id', array('name' => $name, 'plugin' => $plugin))) {
            if ($value===null) {
                $DB->delete_records('config_plugins', array('name' => $name, 'plugin' => $plugin));
            } else {
                $DB->set_field('config_plugins', 'value', $value, array('id' => $id));
            }
        } else {
            if ($value !== null) {
                $config = new stdClass();
                $config->plugin = $plugin;
                $config->name   = $name;
                $config->value  = $value;
                $DB->insert_record('config_plugins', $config, false);
            }
        }
        cache_helper::invalidate_by_definition('core', 'config', array(), $plugin);
    }

    return true;
}

/**
 * Get configuration values from the global config table
 * or the config_plugins table.
 *
 * If called with one parameter, it will load all the config
 * variables for one plugin, and return them as an object.
 *
 * If called with 2 parameters it will return a string single
 * value or false if the value is not found.
 *
 * NOTE: this function is called from lib/db/upgrade.php
 *
 * @static string|false $siteidentifier The site identifier is not cached. We use this static cache so
 *     that we need only fetch it once per request.
 * @param string $plugin full component name
 * @param string $name default null
 * @return mixed hash-like object or single value, return false no config found
 * @throws dml_exception
 */
function get_con…

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