public static function raise($newlimit = 0) {
        global $CFG;

        // Special behaviour in unit tests so that we can check the value.
        if (PHPUNIT_TEST) {
            self::$unittestdata[] = $newlimit;
        }

        // If the time limit has already been set to 'infinite', ignore. Also do
        // nothing in CLI scripts (including unit testing) which are set to
        // infinite by default.
        if (self::$currentend === 0 || CLI_SCRIPT) {
            return;
        }

        // Maximum time limit can be set in config. This can be useful for front-end
        // server systems; if the front-end server has a timeout without receiving
        // data, it's helpful to set this timeout lower to ensure that a suitable
        // error gets logged.
        if (!empty($CFG->maxtimelimit)) {
            $realtimeout = max(1, $CFG->maxtimelimit);
            if ($newlimit === 0) {
                $newlimit = $realtimeout;
            } else {
                $newlimit = min($newlimit, $realtimeout);
            }
        }

        // If new time limit is infinite, just set that.
        if ($newlimit === 0) {
            self::$currentend = 0;
            @set_time_limit(0);
            return;
        }

        // Calculate time limits to make sure it's longer than previous.
        $now = time();
        $newend = $now + $newlimit;
        if (self::$currentend !== -1 && self::$currentend > $newend) {
            // Existing time limit is already longer, so do nothing.
            return;
        }

        // Set time limit and update current value.
        @set_time_limit($newlimit);
        self::$currentend = $newend;
    }