Regular Expressions

[iwato]

The following code snippet contains a subpattern that I do not understand. I am hoping that someone can explain what it is looking for.The Code Snippet

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

The Poorly Understood Subpattern: ^(?:http://)?What I understand:The pattern (? followed by certain characters can indicate a variety of different assertions.A pair of colons wrapped around a name indicates the presence of a named character class.As neither of these appear to apply here; however, I am lost as to how to interpret the above subpattern. Can someone help?Roddy

[mcampbell]

The Poorly Understood Subpattern: ^(?:http://)?

(?: indicates that the subpattern will not be captured. The ^ matches the start of the string, and the ? after the first subpattern indicates that it is optional. The only subpattern captured will be the second, matching "www.php.net".

[iwato]

(?: indicates that the subpattern will not be captured.

(?:Bingo!Many thanks!Roddy