check if a string is a URL [duplicate]

Answer 1

http://www.php.net/manual/en/function.preg-match.php#93824

but your example URL is over simplified, (\w+)\.(\w+) would match it. somebody else mentioned filter_var which is simply a filter_var($url, FILTER_VALIDATE_URL) but it doesn't seem to like non-ascii characters so, beware...