check if is a url

check_url.php

<?php 
public function checkURL($url) {
        $reg = '%^(?:(?:https?|ftp)://)(?:\S+(?::\S*)?@|\d{1,3}(?:\.\d{1,3}){3}|(?:(?:[a-z\d\x{00a1}-\x{ffff}]+-?)*[a-z\d\x{00a1}-\x{ffff}]+)(?:\.(?:[a-z\d\x{00a1}-\x{ffff}]+-?)*[a-z\d\x{00a1}-\x{ffff}]+)*(?:\.[a-z\x{00a1}-\x{ffff}]{2,6}))(?::\d+)?(?:[^\s]*)?$%iu';
        
        $url = htmlspecialchars(trim($url));
        
        if(preg_match($reg,$url))
            return true;
        else
        {
            $url = "http://".$url;
            
            return (preg_match($reg,$url)) ? true : false;
        }
    }
?>