<?php

$url = "Нужный адрес";  

if (preg_match('/^(http|https|ftp)://([A-Z0-9][A- Z0-9_-]*(?:.[A-Z0-9][A-Z0-9_-]*)+):?(d+)?/?/i' , $url)) {  

echo "Your url is ok.";  

} else {  

echo "Wrong url.";  

}

?>