regex help needed - Please

I need to validate a user supplied URL, if it doesn't begin with http or https, I would like to add it. it can be any type of domain, but anything after the TLD needs to be stripped off, so

www.disdomain.com/index.html

Code (markup):

would become

http://www.disdomain.com

Code (markup):

I have a regular expression that I have made myself, but I'm pretty new to regex, so I don't know if it would even work

^((http|https|ftp):\/\/){1}
(
([a-zA-Z0-9]([a-zA-Z0-9_-]\.)*)
(([a-zA-Z0-9][a-zA-Z0-9_-]*)+ \/?)$
)

Code (markup):

If that regex is good, how would I go about stripping the end of the URL, anything including a slash after the TLD and after the slash?

 

function formatURL( $url )
{
  if( !preg_match( "/^http(s)?/si", trim($url )) )
  {
    $url = "http://" . trim($url);
  }
  $url = parse_url( $url );
  return $url['scheme'] . "://" . $url['host'];
}
echo formatURL( "google.com/index.php?req=e" );

PHP:

That'll work .....

 

That's perfect. Thank you very much.

I tried giving you rep, but it seems as though I've already given you rep recently.

Just one more question, if you don't mind. In the regex above, the /si, I know the i makes it case insensitive, but what about the s?

 

force of habbit, probably not needed :

http://php.net/manual/en/reference.pcre.pattern.modifiers.php