function make_url($string){
	$hack = "|(\[url\])(.*?)(\[/url\])|";
	$code = "<a href=\"\\2\">\\2</a>";
	return preg_replace($hack,$code,$string);
}

$data[$nameloop+3] = "[url]http://www.blah.de[/url]";
echo make_url($data[$nameloop+3]);