DZ 这一段代码的用意是什么啊

$PHP_SELF = dhtmlspecialchars($_SERVER['PHP_SELF'] ? $_SERVER['PHP_SELF'] : $_SERVER['SCRIPT_NAME']);

function dhtmlspecialchars($string) {

        if(is_array($string)) {

                foreach($string as $key => $val) {

                        $string[$key] = dhtmlspecialchars($val);

                }

        } else {

                $string = preg_replace('/&((#(\d{3,5}|x[a-fA-F0-9]{4}));)/', '&\\1',str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $string));

                //$string = preg_replace('/&((#(\d{3,5}|x[a-fA-F0-9]{4})|[a-zA-Z][a-z0-9]{2,5});)/', '&\\1',

                

        }

        return $string;

}