class AR {
    //make $dbh so index can set it;
    public $dbh;
    public function changeTask($task) {
        //make sure task is set and is a string.
        if(isset($task) && is_string($task)) {
            //switch task
            switch($task) {
                case 'version_check':
                    //make sure the method exists before calling it :)
                    if(method_exists(__CLASS__,"version_check")) {
                        $this->version_check();
                    }
                break;
            }
        }
    }
}