PHP :

<?php

// The Regular Expression filter

$reg_exUrl = "/(http|https|ftp|ftps)\:\/\/[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(\/\S*)?/";

// The Text you want to filter for urls

$text = "The text you want to filter goes here. http://google.com";

// Check if there is a url in the text

if(preg_match($reg_exUrl, $text, $url)) {

       // make the urls hyper links

       echo preg_replace($reg_exUrl, "<a href="{$url[0]}">{$url[0]}</a> ", $text);

} else {

       // if no urls in the text just return the text

       echo $text;

}

?>