URL detection and split it into parts, each part is optional minus the hostname.

is_url.php

<?php
        function is_url($text)
        {
                if (preg_match('/((?P<protocol>[a-z]{3,6}):\/\/)?((?P<userpass>[a-z]+:[a-z]+|[a-z]+)@)?(?P<hostname>[a-z0-9.-]+\.[a-z]{2,6})(:(?P<port>[0-9]+))?(?P<path>\/.)?/i', $text, $matches))
                {
                        $ret = array();
                        foreach ($matches as $key => $value)
                        {
                                if (!is_numeric($key) && $value != '')
                                {
                                        $ret[$key] = $value;
                                }
                        }
                        return $ret;
                }
                return false;
        }

?>