/lib/weblib.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/>.

/**
 * Library of functions for web output
 *
 * Library of all general-purpose Moodle PHP functions and constants
 * that produce HTML output
 *
 * Other main libraries:
 * - datalib.php - functions that access the database.
 * - moodlelib.php - general-purpose Moodle functions.
 *
 * @package    core
 * @subpackage lib
 * @copyright  1999 onwards Martin Dougiamas {@link http://moodle.com}
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

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

// Constants.

// Define text formatting types ... eventually we can add Wiki, BBcode etc.

/**
 * Does all sorts of transformations and filtering.
 */
define('FORMAT_MOODLE',   '0');

/**
 * Plain HTML (with some tags stripped).
 */
define('FORMAT_HTML',     '1');

/**
 * Plain text (even tags are printed in full).
 */
define('FORMAT_PLAIN',    '2');

/**
 * Wiki-formatted text.
 * Deprecated: left here just to note that '3' is not used (at the moment)
 * and to catch any latent wiki-like text (which generates an error)
 * @deprecated since 2005!
 */
define('FORMAT_WIKI',     '3');

/**
 * Markdown-formatted text http://daringfireball.net/projects/markdown/
 */
define('FORMAT_MARKDOWN', '4');

/**
 * A moodle_url comparison using this flag will return true if the base URLs match, params are ignored.
 */
define('URL_MATCH_BASE', 0);

/**
 * A moodle_url comparison using this flag will return true if the base URLs match and the params of url1 are part of url2.
 */
define('URL_MATCH_PARAMS', 1);

/**
 * A moodle_url comparison using this flag will return true if the two URLs are identical, except for the order of the params.
 */
define('URL_MATCH_EXACT', 2);

// Functions.

/**
 * Add quotes to HTML characters.
 *
 * Returns $var with HTML characters (like "<", ">", etc.) properly quoted.
 * Related function {@link p()} simply prints the output of this function.
 *
 * @param string $var the string potentially containing HTML characters
 * @return string
 */
function s($var) {

    if ($var === false) {
        return '0';
    }

    return preg_replace('/&amp;#(\d+|x[0-9a-f]+);/i', '&#$1;',
            htmlspecialchars($var, ENT_QUOTES | ENT_HTML401 | ENT_SUBSTITUTE));
}

/**
 * Add quotes to HTML characters.
 *
 * Prints $var with HTML characters (like "<", ">", etc.) properly quoted.
 * This function simply calls & displays {@link s()}.
 * @see s()
 *
 * @param string $var the string potentially containing HTML characters
 * @return string
 */
function p($var) {
    echo s($var);
}

/**
 * Does proper javascript quoting.
 *
 * Do not use addslashes anymore, because it does not work when magic_quotes_sybase is enabled.
 *
 * @param mixed $var String, Array, or Object to add slashes to
 * @return mixed quoted result
 */
function addslashes_js($var) {
    if (is_string($var)) {
        $var = str_replace('\\', '\\\\', $var);
        $var = str_replace(array('\'', '"', "\n", "\r", "\0"), array('\\\'', '\\"', '\\n', '\\r', '\\0'), $var);
        $var = str_replace('</', '<\/', $var);   // XHTML compliance.
    } else if (is_array($var)) {
        $var = array_map('addslashes_js', $var);
    } else if (is_object($var)) {
        $a = get_object_vars($var);
        foreach ($a as $key => $value) {
            $a[$key] = addslashes_js($value);
        }
        $var = (object)$a;
    }
    return $var;
}

/**
 * Remove query string from url.
 *
 * Takes in a URL and returns it without the querystring portion.
 *
 * @param string $url the url which may have a query string attached.
 * @return string The remaining URL.
 */
function strip_querystring($url) {

    if ($commapos = strpos($url, '?')) {
        return substr($url, 0, $commapos);
    } else {
        return $url;
    }
}

/**
 * Returns the name of the current script, WITH the querystring portion.
 *
 * This function is necessary because PHP_SELF and REQUEST_URI and SCRIPT_NAME
 * return different things depending on a lot of things like your OS, Web
 * server, and the way PHP is compiled (ie. as a CGI, module, ISAPI, etc.)
 * <b>NOTE:</b> This function returns false if the global variables needed are not set.
 *
 * @return mixed String or false if the global variables needed are not set.
 */
function me() {
    global $ME;
    return $ME;
}

/**
 * Guesses the full URL of the current script.
 *
 * This function is using $PAGE->url, but may fall back to $FULLME which
 * is constructed from  PHP_SELF and REQUEST_URI or SCRIPT_NAME
 *
 * @return mixed full page URL string or false if unknown
 */
function qualified_me() {
    global $FULLME, $PAGE, $CFG;

    if (isset($PAGE) and $PAGE->has_set_url()) {
        // This is the only recommended way to find out current page.
        return $PAGE->url->out(false);

    } else {
        if ($FULLME === null) {
            // CLI script most probably.
            return false;
        }
        if (!empty($CFG->sslproxy)) {
            // Return only https links when using SSL proxy.
            return preg_replace('/^http:/', 'https:', $FULLME, 1);
        } else {
            return $FULLME;
        }
    }
}

/**
 * Determines whether or not the Moodle site is being served over HTTPS.
 *
 * This is done simply by checking the value of $CFG->wwwroot, which seems
 * to be the only reliable method.
 *
 * @return boolean True if site is served over HTTPS, false otherwise.
 */
function is_https() {
    global $CFG;

    return (strpos($CFG->wwwroot, 'https://') === 0);
}

/**
 * Returns the cleaned local URL of the HTTP_REFERER less the URL query string parameters if required.
 *
 * @param bool $stripquery if true, also removes the query part of the url.
 * @return string The resulting referer or empty string.
 */
function get_local_referer($stripquery = true) {
    if (isset($_SERVER['HTTP_REFERER'])) {
        $referer = clean_param($_SERVER['HTTP_REFERER'], PARAM_LOCALURL);
        if ($stripquery) {
            return strip_querystring($referer);
        } else {
            return $referer;
        }
    } else {
        return '';
    }
}

/**
 * Class for creating and manipulating urls.
 *
 * It can be used in moodle pages where config.php has been included without any further includes.
 *
 * It is useful for manipulating urls with long lists of params.
 * One situation where it will be useful is a page which links to itself to perform various actions
 * and / or to process form data. A moodle_url object :
 * can be created for a page to refer to itself with all the proper get params being passed from page call to
 * page call and methods can be used to output a url including all the params, optionally adding and overriding
 * params and can also be used to
 *     - output the url without any get params
 *     - and output the params as hidden fields to be output within a form
 *
 * @copyright 2007 jamiesensei
 * @link http://docs.moodle.org/dev/lib/weblib.php_moodle_url See short write up here
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @package core
 */
class moodle_url {

    /**
     * Scheme, ex.: http, https
     * @var string
     */
    protected $scheme = '';

    /**
     * Hostname.
     * @var string
     */
    protected $host = '';

    /**
     * Port number, empty means default 80 or 443 in case of http.
     * @var int
     */
    protected $port = '';

    /**
     * Username for http auth.
     * @var string
     */
    protected $user = '';

    /**
     * Password for http auth.
     * @var string
     */
    protected $pass = '';

    /**
     * Script path.
     * @var string
     */
    protected $path = '';

    /**
     * Optional slash argument value.
     * @var string
     */
    protected $slashargument = '';

    /**
     * Anchor, may be also empty, null means none.
     * @var string
     */
    protected $anchor = null;

    /**
     * Url parameters as associative array.
     * @var array
     */
    protected $params = array();

    /**
     * Create new instance of moodle_url.
     *
     * @param moodle_url|string $url - moodle_url means make a copy of another
     *      moodle_url and change parameters, string means full url or shortened
     *      form (ex.: '/course/view.php'). It is strongly encouraged to not include
     *      query string because it may result in double encoded values. Use the
     *      $params instead. For admin URLs, just use /admin/script.php, this
     *      class takes care of the $CFG->admin issue.
     * @param array $params these params override current params or add new
     * @param string $anchor The anchor to use as part of the URL if there is one.
     * @throws moodle_exception
     */
    public function __construct($url, array $params = null, $anchor = null) {
        global $CFG;

        if ($url instanceof moodle_url) {
            $this->scheme = $url->scheme;
            $this->host = $url->host;
            $this->port = $url->port;
            $this->user = $url->user;
            $this->pass = $url->pass;
            $this->path = $url->path;
            $this->slashargument = $url->slashargument;
            $this->params = $url->params;
            $this->anchor = $url->anchor;

        } else {
            // Detect if anchor used.
            $apos = strpos($url, '#');
            if ($apos !== false) {
                $anchor = substr($url, $apos);
                $anchor = ltrim($anchor, '#');
                $this->set_anchor($anchor);
                $url = substr($url, 0, $apos);
            }

            // Normalise shortened form of our url ex.: '/course/view.php'.
            if (strpos($url, '/') === 0) {
                $url = $CFG->wwwroot.$url;
            }

            if ($CFG->admin !== 'admin') {
                if (strpos($url, "$CFG->wwwroot/admin/") === 0) {
                    $url = str_replace("$CFG->wwwroot/admin/", "$CFG->wwwroot/$CFG->admin/", $url);
                }
            }

            // Parse the $url.
            $parts = parse_url($url);
            if ($parts === false) {
                throw new moodle_exception('invalidurl');
            }
            if (isset($parts['query'])) {
                // Note: the values may not be correctly decoded, url parameters should be always passed as array.
                parse_str(str_replace('&amp;', '&', $parts['query']), $this->params);
            }
            unset($parts['query']);
            foreach ($parts as $key => $value) {
                $this->$key = $value;
            }

            // Detect slashargument value from path - we do not support directory names ending with .php.
            $pos = strpos($this->path, '.php/');
            if ($pos !== false) {
                $this->slashargument = substr($this->path, $pos + 4);
                $this->path = substr($this->path, 0, $pos + 4);
            }
        }

        $this->params($params);
        if ($anchor !== null) {
            $this->anchor = (string)$anchor;
        }
    }

    /**
     * Add an array of params to the params for this url.
     *
     * The added params override existing ones if they have the same name.
     *
     * @param array $params Defaults to null. If null then returns all params.
     * @return array Array of Params for url.
     * @throws coding_exception
     */
    public function params(array $params = null) {
        $params = (array)$params;

        foreach ($params as $key => $value) {
            if (is_int($key)) {
                throw new coding_exception('Url parameters can not have numeric keys!');
            }
            if (!is_string($value)) {
                if (is_array($value)) {
                    throw new coding_exception('Url parameters values can not be arrays!');
                }
                if (is_object($value) and !method_exists($value, '__toString')) {
                    throw new coding_exception('Url parameters values can not be objects, unless __toString() is defined!');
                }
            }
            $this->params[$key] = (string)$value;
        }
        return $this->params;
    }

    /**
     * Remove all params if no arguments passed.
     * Remove selected params if arguments are passed.
     *
     * Can be called as either remove_params('param1', 'param2')
     * or remove_params(array('param1', 'param2')).
     *
     * @param string[]|string $params,... either an array of param names, or 1..n string params to remove as args.
     * @return array url parameters
     */
    public function remove_params($params = null) {
        if (!is_array($params)) {
            $params = func_get_args();
        }
        foreach ($params as $param) {
            unset($this->params[$param]);
        }
        return $this->params;
    }

    /**
     * Remove all url parameters.
     *
     * @todo remove the unused param.
     * @param array $params Unused param
     * @return void
     */
    public function remove_all_params($params = null) {
        $this->params = array();
        $this->slashargument = '';
    }

    /**
     * Add a param to the params for this url.
     *
     * The added param overrides existing one if they have the same name.
     *
     * @param string $paramname name
     * @param string $newvalue Param value. If new value specified current value is overriden or parameter is added
     * @return mixed string parameter value, null if parameter does not exist
     */
    public function param($paramname, $newvalue = '') {
        if (func_num_args() > 1) {
            // Set new value.
            $this->params(array($paramname => $newvalue));
        }
        if (isset($this->params[$paramname])) {
            return $this->params[$paramname];
        } else {
            return null;
        }
    }

    /**
     * Merges parameters and validates them
     *
     * @param array $overrideparams
     * @return array merged parameters
     * @throws coding_exception
     */
    protected function merge_overrideparams(array $overrideparams = null) {
        $overrideparams = (array)$overrideparams;
        $params = $this->params;
        foreach ($overrideparams as $key => $value) {
            if (is_int($key)) {
                throw new coding_exception('Overridden parameters can not have numeric keys!');
            }
            if (is_array($value)) {
                throw new coding_exception('Overridden parameters values can not be arrays!');
            }
            if (is_object($value) and !method_exists($value, '__toString')) {
                throw new coding_exception('Overridden parameters values can not be objects, unless __toString() is defined!');
            }
            $params[$key] = (string)$value;
        }
        return $params;
    }

    /**
     * Get the params as as a query string.
     *
     * This method should not be used outside of this method.
     *
     * @param bool $escaped Use &amp; as params separator instead of plain &
     * @param array $overrideparams params to add to the output params, these
     *      override existing ones with the same name.
     * @return string query string that can be added to a url.
     */
    public function get_query_string($escaped = true, array $overrideparams = null) {
        $arr = array();
        if ($overrideparams !== null) {
            $params = $this->merge_overrideparams($overrideparams);
        } else {
            $params = $this->params;
        }
        foreach ($params as $key => $val) {
            if (is_array($val)) {
                foreach ($val as $index => $value) {
                    $arr[] = rawurlencode($key.'['.$index.']')."=".rawurlencode($value);
                }
            } else {
                if (isset($val) && $val !== '') {
                    $arr[] = rawurlencode($key)."=".rawurlencode($val);
                } else {
                    $arr[] = rawurlencode($key);
                }
            }
        }
        if ($escaped) {
            return implode('&amp;', $arr);
        } else {
            return implode('&', $arr);
        }
    }

    /**
     * Shortcut for printing of encoded URL.
     *
     * @return string
     */
    public function __toString() {
        return $this->out(true);
    }

    /**
     * Output url.
     *
     * If you use the returned URL in HTML code, you want the escaped ampersands. If you use
     * the returned URL in HTTP headers, you want $escaped=false.
     *
     * @param bool $escaped Use &amp; as params separator instead of plain &
     * @param array $overrideparams params to add to the output url, these override existing ones with the same name.
     * @return string Resulting URL
     */
    public function out($escaped = true, array $overrideparams = null) {

        global $CFG;

        if (!is_bool($escaped)) {
            debugging('Escape parameter must be of type boolean, '.gettype($escaped).' given instead.');
        }

        $url = $this;

        // Allow url's to be rewritten by a plugin.
        if (isset($CFG->urlrewriteclass) && !isset($CFG->upgraderunning)) {
            $class = $CFG->urlrewriteclass;
            $pluginurl = $class::url_rewrite($url);
            if ($pluginurl instanceof moodle_url) {
                $url = $pluginurl;
            }
        }

        return $url->raw_out($escaped, $overrideparams);

    }

    /**
     * Output url without any rewrites
     *
     * This is identical in signature and use to out() but doesn't call the rewrite handler.
     *
     * @param bool $escaped Use &amp; as params separator instead of plain &
     * @param array $overrideparams params to add to the output url, these override existing ones with the same name.
     * @return string Resulting URL
     */
    public function raw_out($escaped = true, array $overrideparams = null) {
        if (!is_bool($escaped)) {
            debugging('Escape parameter must be of type boolean, '.gettype($escaped).' given instead.');
        }

        $uri = $this->out_omit_querystring().$this->slashargument;

        $querystring = $this->get_query_string($escaped, $overrideparams);
        if ($querystring !== '') {
            $uri .= '?' . $querystring;
        }
        if (!is_null($this->anchor)) {
            $uri .= '#'.$this->anchor;
        }

        return $uri;
    }

    /**
     * Returns url without parameters, everything before '?'.
     *
     * @param bool $includeanchor if {@link self::anchor} is defined, should it be returned?
     * @return string
     */
    public function out_omit_querystring($includeanchor = false) {

        $uri = $this->scheme ? $this->scheme.':'.((strtolower($this->scheme) == 'mailto') ? '':'//'): '';
        $uri .= $this->user ? $this->user.($this->pass? ':'.$this->pass:'').'@':'';
        $uri .= $this->host ? $this->host : '';
        $uri .= $this->port ? ':'.$this->port : '';
        $uri .= $this->path ? $this->path : '';
        if ($includeanchor and !is_null($this->anchor)) {
            $uri .= '#' . $this->anchor;
        }

        return $uri;
    }

    /**
     * Compares this moodle_url with another.
     *
     * See documentation of constants for an explanation of the comparison flags.
     *
     * @param moodle_url $url The moodle_url object to compare
     * @param int $matchtype The type of comparison (URL_MATCH_BASE, URL_MATCH_PARAMS, URL_MATCH_EXACT)
     * @return bool
     */
    public function compare(moodle_url $url, $matchtype = URL_MATCH_EXACT) {

        $baseself = $this->out_omit_querystring();
        $baseother = $url->out_omit_querystring();

        // Append index.php if there is no specific file.
        if (substr($baseself, -1) == '/') {
            $baseself .= 'index.php';
        }
        if (substr($baseother, -1) == '/') {
            $baseother .= 'index.php';
        }

        // Compare the two base URLs.
        if ($baseself != $baseother) {
            return false;
        }

        if ($matchtype == URL_MATCH_BASE) {
            return true;
        }

        $urlparams = $url->params();
        foreach ($this->params() as $param => $value) {
            if ($param == 'sesskey') {
                continue;
            }
            if (!array_key_exists($param, $urlparams) || $urlparams[$param] != $value) {
                return false;
            }
        }

        if ($matchtype == URL_MATCH_PARAMS) {
            return true;
        }

        foreach ($urlparams as $param => $value) {
            if ($param == 'sesskey') {
                continue;
            }
            if (!array_key_exists($param, $this->params()) || $this->param($param) != $value) {
                return false;
            }
        }

        if ($url->anchor !== $this->anchor) {
            return false;
        }

        return true;
    }

    /**
     * Sets the anchor for the URI (the bit after the hash)
     *
     * @param string $anchor null means remove previous
     */
    public function set_anchor($anchor) {
        if (is_null($anchor)) {
            // Remove.
            $this->anchor = null;
        } else if ($anchor === '') {
            // Special case, used as empty link.
            $this->anchor = '';
        } else if (preg_match('|[a-zA-Z\_\:][a-zA-Z0-9\_\-\.\:]*|', $anchor)) {
            // Match the anchor against the NMTOKEN spec.
            $this->anchor = $anchor;
        } else {
            // Bad luck, no valid anchor found.
            $this->anchor = null;
        }
    }

    /**
     * Sets the scheme for the URI (the bit before ://)
     *
     * @param string $scheme
     */
    public function set_scheme($scheme) {
        // See http://www.ietf.org/rfc/rfc3986.txt part 3.1.
        if (preg_match('/^[a-zA-Z][a-zA-Z0-9+.-]*$/', $scheme)) {
            $this->scheme = $scheme;
        } else {
            throw new coding_exception('Bad URL scheme.');
        }
    }

    /**
     * Sets the url slashargument value.
     *
     * @param string $path usually file path
     * @param string $parameter name of page parameter if slasharguments not supported
     * @param bool $supported usually null, then it depends on $CFG->slasharguments, use true or false for other servers
     * @return void
     */
    public function set_slashargument($path, $parameter = 'file', $supported = null) {
        global $CFG;
        if (is_null($supported)) {
            $supported = !empty($CFG->slasharguments);
        }

        if ($supported) {
            $parts = explode('/', $path);
            $parts = array_map('rawurlencode', $parts);
            $path  = implode('/', $parts);
            $this->slashargument = $path;
            unset($this->params[$parameter]);

        } else {
            $this->slashargument = '';
            $this->params[$parameter] = $path;
        }
    }

    // Static factory methods.

    /**
     * General moodle file url.
     *
     * @param string $urlbase the script serving the file
     * @param string $path
     * @param bool $forcedownload
     * @return moodle_url
     */
    public static function make_file_url($urlbase, $path, $forcedownload = false) {
        $params = array();
        if ($forcedownload) {
            $params['forcedownload'] = 1;
        }
        $url = new moodle_url($urlbase, $params);
        $url->set_slashargument($path);
        return $url;
    }

    /**
     * Factory method for creation of url pointing to plugin file.
     *
     * Please note this method can be used only from the plugins to
     * create urls of own files, it must not be used outside of plugins!
     *
     * @param int $contextid
     * @param string $component
     * @param string $area
     * @param int $itemid
     * @param string $pathname
     * @param string $filename
     * @param bool $forcedownload
     * @param mixed $includetoken Whether to use a user token when displaying this group image.
     *                True indicates to generate a token for current user, and integer value indicates to generate a token for the
     *                user whose id is the value indicated.
     *                If the group picture is included in an e-mail or some other location where the audience is a specific
     *                user who will not be logged in when viewing, then we use a token to authenticate the user.
     * @return moodle_url
     */
    public static function make_pluginfile_url($contextid, $component, $area, $itemid, $pathname, $filename,
                                               $forcedownload = false, $includetoken = false) {
        global $CFG, $USER;

        $path = [];

        if ($includetoken) {
            $urlbase = "$CFG->wwwroot/tokenpluginfile.php";
            $userid = $includetoken === true ? $USER->id : $includetoken;
            $token = get_user_key('core_files', $userid);
            if ($CFG->slasharguments) {
                $path[] = $token;
            }
        } else {
            $urlbase = "$CFG->wwwroot/pluginfile.php";
        }
        $path[] = $contextid;
        $path[] = $component;
        $path[] = $area;

        if ($itemid !== null) {
            $path[] = $itemid;
        }

        $path = "/" . implode('/', $path) . "{$pathname}{$filename}";

        $url = self::make_file_url($urlbase, $path, $forcedownload, $includetoken);
        if ($includetoken && empty($CFG->slasharguments)) {
            $url->param('token', $token);
        }
        return $url;
    }

    /**
     * Factory method for creation of url pointing to plugin file.
     * This method is the same that make_pluginfile_url but pointing to the webservice pluginfile.php script.
     * It should be used only in external functions.
     *
     * @since  2.8
     * @param int $contextid
     * @param string $component
     * @param string $area
     * @param int $itemid
     * @param string $pathname
     * @param string $filename
     * @param bool $forcedownload
     * @return moodle_url
     */
    public static function make_webservice_pluginfile_url($contextid, $component, $area, $itemid, $pathname, $filename,
                                               $forcedownload = false) {
        global $CFG;
        $urlbase = "$CFG->wwwroot/webservice/pluginfile.php";
        if ($itemid === null) {
            return self::make_file_url($urlbase, "/$contextid/$component/$area".$pathname.$filename, $forcedownload);
        } else {
            return self::make_file_url($urlbase, "/$contextid/$component/$area/$itemid".$pathname.$filename, $forcedownload);
        }
    }

    /**
     * Factory method for creation of url pointing to draft file of current user.
     *
     * @param int $draftid draft item id
     * @param string $pathname
     * @param string $filename
     * @param bool $forcedownload
     * @return moodle_url
     */
    public static function make_draftfile_url($draftid, $pathname, $filename, $forcedownload = false) {
        global $CFG, $USER;
        $urlbase = "$CFG->wwwroot/draftfile.php";
        $context = context_user::instance($USER->id);

        return self::make_file_url($urlbase, "/$context->id/user/draft/$draftid".$pathname.$filename, $forcedownload);
    }

    /**
     * Factory method for creating of links to legacy course files.
     *
     * @param int $courseid
     * @param string $filepath
     * @param bool $forcedownload
     * @return moodle_url
     */
    public static function make_legacyfile_url($courseid, $filepath, $forcedownload = false) {
        global $CFG;

        $urlbase = "$CFG->wwwroot/file.php";
        return self::make_file_url($urlbase, '/'.$courseid.'/'.$filepath, $forcedownload);
    }

    /**
     * Returns URL a relative path from $CFG->wwwroot
     *
     * Can be used for passing around urls with the wwwroot stripped
     *
     * @param boolean $escaped Use &amp; as params separator instead of plain &
     * @param array $overrideparams params to add to the output url, these override existing ones with the same name.
     * @return string Resulting URL
     * @throws coding_exception if called on a non-local url
     */
    public function out_as_local_url($escaped = true, array $overrideparams = null) {
        global $CFG;

        $url = $this->out($escaped, $overrideparams);

        // Url should be equal to wwwroot. If not then throw exception.
        if (($url === $CFG->wwwroot) || (strpos($url, $CFG->wwwroot.'/') === 0)) {
            $localurl = substr($url, strlen($CFG->wwwroot));
            return !empty($localurl) ? $localurl : '';
        } else {
            throw new coding_exception('out_as_local_url called on a non-local URL');
        }
    }

    /**
     * Returns the 'path' portion of a URL. For example, if the URL is
     * http://www.example.org:447/my/file/is/here.txt?really=1 then this will
     * return '/my/file/is/here.txt'.
     *
     * By default the path includes slash-arguments (for example,
     * '/myfile.php/extra/arguments') so it is what you would expect from a
     * URL path. If you don't want this behaviour, you can opt to exclude the
     * slash arguments. (Be careful: if the $CFG variable slasharguments is
     * disabled, these URLs will have a different format and you may need to
     * look at the 'file' parameter too.)
     *
     * @param bool $includeslashargument If true, includes slash arguments
     * @return string Path of URL
     */
    public function get_path($includeslashargument = true) {
        return $this->path . ($includeslashargument ? $this->slashargument : '');
    }

    /**
     * Returns a given parameter value from the URL.
     *
     * @param string $name Name of parameter
     * @return string Value of parameter or null if not set
     */
    public function get_param($name) {
        if (array_key_exists($name, $this->params)) {
            return $this->params[$name];
        } else {
            return null;
        }
    }

    /**
     * Returns the 'scheme' portion of a URL. For example, if the URL is
     * http://www.example.org:447/my/file/is/here.txt?really=1 then this will
     * return 'http' (without the colon).
     *
     * @return string Scheme of the URL.
     */
    public function get_scheme() {
        return $this->scheme;
    }

    /**
     * Returns the 'host' portion of a URL. For example, if the URL is
     * http://www.example.org:447/my/file/is/here.txt?really=1 then this will
     * return 'www.example.org'.
     *
     * @return string Host of the URL.
     */
    public function get_host() {
        return $this->host;
    }

    /**
     * Returns the 'port' portion of a URL. For example, if the URL is
     * http://www.example.org:447/my/file/is/here.txt?really=1 then this will
     * return '447'.
     *
     * @return string Port of the URL.
     */
    public function get_port() {
        return $this->port;
    }
}

/**
 * Determine if there is data waiting to be processed from a form
 *
 * Used on most forms in Moodle to check for data
 * Returns the data as an object, if it's found.
 * This object can be used in foreach loops without
 * casting because it's cast to (array) automatically
 *
 * Checks that submitted POST data exists and returns it as object.
 *
 * @return mixed false or object
 */
function data_submitted() {

    if (empty($_POST)) {
        return false;
    } else {
        return (object)fix_utf8($_POST);
    }
}

/**
 * Given some normal text this function will break up any
 * long words to a given size by inserting the given character
 *
 * It's multibyte savvy and doesn't change anything inside html tags.
 *
 * @param string $string the string to be modified
 * @param int $maxsize maximum length of the string to be returned
 * @param string $cutchar the string used to represent word breaks
 * @return string
 */
function break_up_long_words($string, $maxsize=20, $cutchar=' ') {

    // First of all, save all the tags inside the text to skip them.
    $tags = array();
    filter_save_tags($string, $tags);

    // Process the string adding the cut when necessary.
    $output = '';
    $length = core_text::strlen($string);
    $wordlength = 0;

    for ($i=0; $i<$length; $i++) {
        $char = core_text::substr($string, $i, 1);
        if ($char == ' ' or $char == "\t" or $char == "\n" or $char == "\r" or $char == "<" or $char == ">") {
            $wordlength = 0;
        } else {
            $wordlength++;
            if ($wordlength > $maxsize) {
                $output .= $cutchar;
                $wordlength = 0;
            }
        }
        $output .= $char;
    }

    // Finally load the tags back again.
    if (!empty($tags)) {
        $output = str_replace(array_keys($tags), $tags, $output);
    }

    return $output;
}

/**
 * Try and close the current window using JavaScript, either immediately, or after a delay.
 *
 * Echo's out the resulting XHTML & javascript
 *
 * @param integer $delay a delay in seconds before closing the window. Default 0.
 * @param boolean $reloadopener if true, we will see if this window was a pop-up, and try
 *      to reload the parent window before this one closes.
 */
function close_window($delay = 0, $reloadopener = false) {
    global $PAGE, $OUTPUT;

    if (!$PAGE->headerprinted) {
        $PAGE->set_title(get_string('closewindow'));
        echo $OUTPUT->header();
    } else {
        $OUTPUT->container_end_all(false);
    }

    if ($reloadopener) {
        // Trigger the reload immediately, even if the reload is after a delay.
        $PAGE->requires->js_function_call('window.opener.location.reload', array(true));
    }
    $OUTPUT->notification(get_string('windowclosing'), 'notifysuccess');

    $PAGE->requires->js_function_call('close_window', array(new stdClass()), false, $delay);

    echo $OUTPUT->footer();
    exit;
}

/**
 * Returns a string containing a link to the user documentation for the current page.
 *
 * Also contains an icon by default. Shown to teachers and admin only.
 *
 * @param string $text The text to be displayed for the link
 * @return string The link to user documentation for this current page
 */
function page_doc_link($text='') {
    global $OUTPUT, $PAGE;
    $path = page_get_doc_link_path($PAGE);
    if (!$path) {
        return '';
    }
    return $OUTPUT->doc_link($path, $text);
}

/**
 * Returns the path to use when constructing a link to the docs.
 *
 * @since Moodle 2.5.1 2.6
 * @param moodle_page $page
 * @return string
 */
function page_get_doc_link_path(moodle_page $page) {
    global $CFG;

    if (empty($CFG->docroot) || during_initial_install()) {
        return '';
    }
    if (!has_capability('moodle/site:doclinks', $page->context)) {
        return '';
    }

    $path = $page->docspath;
    if (!$path) {
        return '';
    }
    return $path;
}


/**
 * Validates an email to make sure it makes sense.
 *
 * @param string $address The email address to validate.
 * @return boolean
 */
function validate_email($address) {
    global $CFG;
    require_once($CFG->libdir.'/phpmailer/moodle_phpmailer.php');

    return moodle_phpmailer::validateAddress($address) && !preg_match('/[<>]/', $address);
}

/**
 * Extracts file argument either from file parameter or PATH_INFO
 *
 * Note: $scriptname parameter is not needed anymore
 *
 * @return string file path (only safe characters)
 */
function get_file_argument() {
    global $SCRIPT;

    $relativepath = false;
    $hasforcedslashargs = false;

    if (isset($_SERVER['REQUEST_URI']) && !empty($_SERVER['REQUEST_URI'])) {
        // Checks whether $_SERVER['REQUEST_URI'] contains '/pluginfile.php/'
        // instead of '/pluginfile.php?', when serving a file from e.g. mod_imscp or mod_scorm.
        if ((strpos($_SERVER['REQUEST_URI'], '/pluginfile.php/') !== false)
                && isset($_SERVER['PATH_INFO']) && !empty($_SERVER['PATH_INFO'])) {
            // Exclude edge cases like '/pluginfile.php/?file='.
            $args = explode('/', ltrim($_SERVER['PATH_INFO'], '/'));
            $hasforcedslashargs = (count($args) > 2); // Always at least: context, component and filearea.
        }
    }
    if (!$hasforcedslashargs) {
        $relativepath = optional_param('file', false, PARAM_PATH);
    }

    if ($relativepath !== false and $relativepath !== '') {
        return $relativepath;
    }
    $relativepath = false;

    // Then try extract file from the slasharguments.
    if (stripos($_SERVER['SERVER_SOFTWARE'], 'iis') !== false) {
        // NOTE: IIS tends to convert all file paths to single byte DOS encoding,
        //       we can not use other methods because they break unicode chars,
        //       the only ways are to use URL rewriting
        //       OR
        //       to properly set the 'FastCGIUtf8ServerVariables' registry key.
        if (isset($_SERVER['PATH_INFO']) and $_SERVER['PATH_INFO'] !== '') {
            // Check that PATH_INFO works == must not contain the script name.
            if (strpos($_SERVER['PATH_INFO'], $SCRIPT) === false) {
                $relativepath = clean_param(urldecode($_SERVER['PATH_INFO']), PARAM_PATH);
            }
        }
    } else {
        // All other apache-like servers depend on PATH_INFO.
        if (isset($_SERVER['PATH_INFO'])) {
            if (isset($_SERVER['SCRIPT_NAME']) and strpos($_SERVER['PATH_INFO'], $_SERVER['SCRIPT_NAME']) === 0) {
                $relativepath = substr($_SERVER['PATH_INFO'], strlen($_SERVER['SCRIPT_NAME']));
            } else {
                $relativepath = $_SERVER['PATH_INFO'];
            }
            $relativepath = clean_param($relativepath, PARAM_PATH);
        }
    }

    return $relativepath;
}

/**
 * Just returns an array of text formats suitable for a popup menu
 *
 * @return array
 */
function format_text_menu() {
    return array (FORMAT_MOODLE => get_string('formattext'),
                  FORMAT_HTML => get_string('formathtml'),
                  FORMAT_PLAIN => get_string('formatplain'),
                  FORMAT_MARKDOWN => get_string('formatmarkdown'));
}

/**
 * Given text in a variety of format codings, this function returns the text as safe HTML.
 *
 * This function should mainly be used for long strings like posts,
 * answers, glossary items etc. For short strings {@link format_string()}.
 *
 * <pre>
 * Options:
 *      trusted     :   If true the string won't be cleaned. Default false required noclean=true.
 *      noclean     :   If true the string won't be cleaned, unless $CFG->forceclean is set. Default false required trusted=true.
 *      nocache     :   If true the strign will not be cached and will be formatted every call. Default false.
 *      filter      :   If true the string will be run through applicable filters as well. Default true.
 *      para        :   If true then the returned string will be wrapped in div tags. Default true.
 *      newlines    :   If true then lines newline breaks will be converted to HTML newline breaks. Default true.
 *      context     :   The context that will be used for filtering.
 *      overflowdiv :   If set to true the formatted text will be encased in a div
 *                      with the class no-overflow before being returned. Default false.
 *      allowid     :   If true then id attributes will not be removed, even when
 *                      using htmlpurifier. Default false.
 *      blanktarget :   If true all <a> tags will have target="_blank" added unless target is explicitly specified.
 * </pre>
 *
 * @staticvar array $croncache
 * @param string $text The text to be formatted. This is raw text originally from user input.
 * @param int $format Identifier of the text format to be used
 *            [FORMAT_MOODLE, FORMAT_HTML, FORMAT_PLAIN, FORMAT_MARKDOWN]
 * @param object/array $options text formatting options
 * @param int $courseiddonotuse deprecated course id, use context option instead
 * @return string
 */
function format_text($text, $format = FORMAT_MOODLE, $options = null, $courseiddonotuse = null) {
    global $CFG, $DB, $PAGE;

    if ($text === '' || is_null($text)) {
        // No need to do any filters and cleaning.
        return '';
    }

    // Detach object, we can not modify it.
    $options = (array)$options;

    if (!isset($options['trusted'])) {
        $options['trusted'] = false;
    }
    if (!isset($options['noclean'])) {
        if ($options['trusted'] and trusttext_active()) {
            // No cleaning if text trusted and noclean not specified.
            $options['noclean'] = true;
        } else {
            $options['noclean'] = false;
        }
    }
    if (!empty($CFG->forceclean)) {
        // Whatever the caller claims, the admin wants all content cleaned anyway.
        $options['noclean'] = false;
    }
    if (!isset($options['nocache'])) {
        $options['nocache'] = false;
    }
    if (!isset($options['filter'])) {
        $options['filter'] = true;
    }
    if (!isset($options['para'])) {
        $options['para'] = true;
    }
    if (!isset($options['newlines'])) {
        $options['newlines'] = true;
    }
    if (!isset($options['overflowdiv'])) {
        $options['overflowdiv'] = false;
    }
    $options['blanktarget'] = !empty($options['blanktarget']);

    // Calculate best context.
    if (empty($CFG->version) or $CFG->version < 2013051400 or during_initial_install()) {
        // Do not filter anything during installation or before upgrade completes.
        $context = null;

    } else if (isset($options['context'])) { // First by explicit passed context option.
        if (is_object($options['context'])) {
            $context = $options['context'];
        } else {
            $context = context::instance_by_id($options['context']);
        }
    } else if ($courseiddonotuse) {
        // Legacy courseid.
        $context = context_course::instance($courseiddonotuse);
    } else {
        // Fallback to $PAGE->context this may be problematic in CLI and other non-standard pages :-(.
        $context = $PAGE->context;
    }

    if (!$context) {
        // Either install/upgrade or something has gone really wrong because context does not exist (yet?).
        $options['nocache'] = true;
        $options['filter']  = false;
    }

    if ($options['filter']) {
        $filtermanager = filter_manager::instance();
        $filtermanager->setup_page_for_filters($PAGE, $context); // Setup global stuff filters may have.
        $filteroptions = array(
            'originalformat' => $format,
            'noclean' => $options['noclean'],
        );
    } else {
        $filtermanager = new null_filter_manager();
        $filteroptions = array();
    }

    switch ($format) {
        case FORMAT_HTML:
            if (!$options['noclean']) {
                $text = clean_text($text, FORMAT_HTML, $options);
            }
            $text = $filtermanager->filter_text($text, $context, $filteroptions);
            break;

        case FORMAT_PLAIN:
            $text = s($text); // Cleans dangerous JS.
            $text = rebuildnolinktag($text);
            $text = str_replace('  ', '&nbsp; ', $text);
            $text = nl2br($text);
            break;

        case FORMAT_WIKI:
            // This format is deprecated.
            $text = '<p>NOTICE: Wiki-like formatting has been removed from Moodle.  You should not be seeing
                     this message as all texts should have been converted to Markdown format instead.
                     Please post a bug report to http://moodle.org/bugs with information about where you
                     saw this message.</p>'.s($text);
            break;

        case FORMAT_MARKDOWN:
            $text = markdown_to_html($text);
            if (!$options['noclean']) {
                $text = clean_text($text, FORMAT_HTML, $options);
            }
            $text = $filtermanager->filter_text($text, $context, $filteroptions);
            break;

        default:  // FORMAT_MOODLE or anything else.
            $text = text_to_html($text, null, $options['para'], $options['newlines']);
            if (!$options['noclean']) {
                $text = clean_text($text, FORMAT_HTML, $options);
            }
            $text = $filtermanager->filter_text($text, $context, $filteroptions);
            break;
    }
    if ($options['filter']) {
        // At this point there should not be any draftfile links any more,
        // this happens when developers forget to post process the text.
        // The only potential problem is that somebody might try to format
        // the text before storing into database which would be itself big bug..
        $text = str_replace("\"$CFG->wwwroot/draftfile.php", "\"$CFG->wwwroot/brokenfile.php#", $text);

        if ($CFG->debugdeveloper) {
            if (strpos($text, '@@PLUGINFILE@@/') !== false) {
                debugging('Before calling format_text(), the content must be processed with file_rewrite_pluginfile_urls()',
                    DEBUG_DEVELOPER);
            }
        }
    }

    if (!empty($options['overflowdiv'])) {
        $text = html_writer::tag('div', $text, array('class' => 'no-overflow'));
    }

    if ($options['blanktarget']) {
        $domdoc = new DOMDocument();
        libxml_use_internal_errors(true);
        $domdoc->loadHTML('<?xml version="1.0" encoding="UTF-8" ?>' . $text);
        libxml_clear_errors();
        foreach ($domdoc->getElementsByTagName('a') as $link) {
            if ($link->hasAttribute('target') && strpos($link->getAttribute('target'), '_blank') === false) {
                continue;
            }
            $link->setAttribute('target', '_blank');
            if (strpos($link->getAttribute('rel'), 'noreferrer') === false) {
                $link->setAttribute('rel', trim($link->getAttribute('rel') . ' noreferrer'));
            }
        }

        // This regex is nasty and I don't like it. The correct way to solve this is by loading the HTML like so:
        // $domdoc->loadHTML($text, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD); however it seems like the libxml
        // version that travis uses doesn't work properly and ends up leaving <html><body>, so I'm forced to use
        // this regex to remove those tags.
        $text = trim(preg_replace('~<(?:!DOCTYPE|/?(?:html|body))[^>]*>\s*~i', '', $domdoc->saveHTML($domdoc->documentElement)));
    }

    return $text;
}

/**
 * Resets some data related to filters, called during upgrade or when general filter settings change.
 *
 * @param bool $phpunitreset true means called from our PHPUnit integration test reset
 * @return void
 */
function reset_text_filters_cache($phpunitreset = false) {
    global $CFG, $DB;

    if ($phpunitreset) {
        // HTMLPurifier does not change, DB is already reset to defaults,
        // nothing to do here, the dataroot was cleared too.
        return;
    }

    // The purge_all_caches() deals with cachedir and localcachedir purging,
    // the individual filter caches are invalidated as necessary elsewhere.

    // Update $CFG->filterall cache flag.
    if (empty($CFG->stringfilters)) {
        set_config('filterall', 0);
        return;
    }
    $installedfilters = core_component::get_plugin_list('filter');
    $filters = explode(',', $CFG->stringfilters);
    foreach ($filters as $filter) {
        if (isset($installedfilters[$filter])) {
            set_config('filterall', 1);
            return;
        }
    }
    set_config('filterall', 0);
}

/**
 * Given a simple string, this function returns the string
 * processed by enabled string filters if $CFG->filterall is enabled
 *
 * This function should be used to print short strings (non html) that
 * need filter processing e.g. activity titles, post subjects,
 * glossary concepts.
 *
 * @staticvar bool $strcache
 * @param string $string The string to be filtered. Should be plain text, expect
 * possibly for multilang tags.
 * @param boolean $striplinks To strip any link in the result text. Moodle 1.8 default changed from false to true! MDL-8713
 * @param array $options options array/object or courseid
 * @return string
 */
function format_string($string, $striplinks = true, $options = null) {
    global $CFG, $PAGE;

    // We'll use a in-memory cache here to speed up repeated strings.
    static $strcache = false;

    if (empty($CFG->version) or $CFG->version < 2013051400 or during_initial_install()) {
        // Do not filter anything during installation or before upgrade completes.
        return $string = strip_tags($string);
    }

    if ($strcache === false or count($strcache) > 2000) {
        // This number might need some tuning to limit memory usage in cron.
        $strcache = array();
    }

    if (is_numeric($options)) {
        // Legacy courseid usage.
        $options  = array('context' => context_course::instance($options));
    } else {
        // Detach object, we can not modify it.
        $options = (array)$options;
    }

    if (empty($options['context'])) {
        // Fallback to $PAGE->context this may be problematic in CLI and other non-standard pages :-(.
        $options['context'] = $PAGE->context;
    } else if (is_numeric($options['context'])) {
        $options['context'] = context::instance_by_id($options['context']);
    }
    if (!isset($options['filter'])) {
        $options['filter'] = true;
    }

    $option…

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