Regular expressions question...

PHP regular expressions need to be deliminated. / is commonly used for this, but anything except an alphanumeric or a \ can be used. You might also see perl style (), {}, [], and <> matching deliminators, but they don't seem to be common in PHP. (And IMO, the [] one is just evil.) Basically everything between the /'s are the regular expression, and various types of modifiers can follow the regex after the deliminator. If the deliminator appears in the regex it needs to be escaped with \.

I think it is simply treat the expression between the two forward slashes, as a single regex statement, although my regex experience is limited, and with python, so this is only a slightly educated guess.

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Original post by SiCrane PHP regular expressions need to be deliminated. / is commonly used for this, but anything except an alphanumeric or a \ can be used. You might also see perl style (), {}, [], and <> matching deliminators, but they don't seem to be common in PHP. (And IMO, the [] one is just evil.) Basically everything between the /'s are the regular expression, and various types of modifiers can follow the regex after the deliminator. If the deliminator appears in the regex it needs to be escaped with \.

I understand it more now, but could you give me some examples? Should I always use these delimiters? What exactly can follow them? Can there be more than one set of delimeters? ("/expression/ something /another expression/"?

Deliminaters should always be used, I'm pretty sure recent versions of PHP will reject regex's without valid deliminators.

Off the top of my head valid modifiers include: i, which makes the regex case insensitive; s, which causes . to match new lines; and S, which optimizes certain classes of regexes if you plan to use them more than once. A PHP reference should have a more complete list.

I'm pretty sure if you try to create a regex with more than one set of deliminators, PHP will reject it, since the second regex will be interpreted as an invalid modifer.

Thanks! I always knew they were usefull but they looked somewhat intimidating. I needed to learn them for the project I am working on right now.