比较简单的

$str = ''; $isMatched = preg_match('/^^((https|http|ftp|rtsp|mms)?://)[^s]+$/', $str, $matches); var_dump($isMatched, $matches);

几乎可以匹配任何网址：

^((https?|ftp|news)://)?([a-z]([a-z0-9-]*[.。])+([a-z]{2}|aero|arpa|biz|com|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel)|(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]).){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]))(/[a-z0-9_-.~]+)*(/([a-z0-9_-.]*)(?[a-z0-9+_-.%=&]*)?)?(#[a-z][a-z0-9_]*)?$

实例：

<script type="text/javascript"> function IsURL(urlString) { regExp = /^((https?|ftp|news)://)?([a-z]([a-z0-9-]*[.。])+([a-z]{2}|aero|arpa|biz|com|coop|edu|gov|info|int|jobs|mil|museum|name|nato|net|org|pro|travel)|(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]).){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5]))(/[a-z0-9_-.~]+)*(/([a-z0-9_-.]*)(?[a-z0-9+_-.%=&]*)?)?(#[a-z][a-z0-9_]*)?$/ if (urlString.match(regExp)) return "is a url"; else return "not a url"; } url = ""; alert(IsURL(url)); </script>