Quick PHP regex question!

[johnnnn]

I'm using the following snippet as an example from the manual:

PHP Code:

preg_match('@^(?:http://)?([^/]+)@i',
    "http://www.php.net/index.html", $matches); 


My question is, what does the ?: before http:// do?
Thanks

[MattF]

It makes the parantheses non capturing.

[Phil Jackson]

i.e. $1 will not equal to 'http://' but to '[^/]+'
without '?:' $1 will equal to 'http://' and $2 will equal to '[^/]+'