PHP-Code:
if(substr_count(strtolower($text),"[url]") >= 1) {
if(!substr_count(strtolower($text),"[url]http://www.") >= 1){
$text = str_replace("[url]www.","[url]http://www.",$text);
}
$text = preg_replace("/\[url\](.*?)\[\/url\]/i","<a href=\"$1\">$1</a>", $text);
}
if(substr_count(strtolower($text),"[url=") >=1){
$text = str_replace("[url=www.","[url=http://www.",$text);
$text = preg_replace("/\[url=(.*?)\](.*?)\[\/url\]/i","<a href=\"$1\">$2</a>", $text);
}
das wäre es in php

also [url][/ url]
und [url=blaba][/ url]