Using regex in PHP

Question

I tried this:

$mtcDatum = preg_match("/[0-9]{2}/[0-9]{2}/[0-9]{4}/", $lnURL);

This returns an error message:

Warning: preg_match() [function.preg-match]: Unknown modifier '['

Why doesn't this work? I'm used to Linux's way of doing regex, does PHP handle regex differently?

Heh, yeah, so based on davearchie & Ben James's answers, the tenth character of your regex is currently the end of your regex, and the function doesn't know what to do with the remaining pile of characters. — Kzqai
– Kzqai, Commented Nov 24, 2009 at 15:57

davearchie · Accepted Answer · 2009-11-24 15:51:26Z

5

PHP syntax is interpreting the "/" character as the end of your pattern. You need to escape the forward slashes:

preg_match("/[0-9]{2}\/[0-9]{2}\/[0-9]{4}/", $lnURL);

answered Nov 24, 2009 at 15:51

davearchie

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Ben James · Accepted Answer · 2009-11-24 16:00:13Z

2

You need a delimiter character around your pattern (this is what separates the pattern from any modifiers). Normally / is used, but as this is part of the string you are trying to match, you can use another character such as #:

$mtcDatum = preg_match("#[0-9]{2}/[0-9]{2}/[0-9]{4}#", $lnURL);

edited Nov 24, 2009 at 16:00

answered Nov 24, 2009 at 15:48

Ben James

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5 Comments

Amarghosh Over a year ago

Shouldn't it be "#[0-9]{2}/[0-9]{2}/[0-9]{4}#"

Amarghosh Over a year ago

And what if I escape the forward slashes "/[0-9]{2}\/[0-9]{2}\/[0-9]{4}/"

Epsilon Prime Over a year ago

Totally right. Note the alternative is to add the slash as the delimiter and then escape all the slashes in your pattern. It's not very readable which is why he suggests choosing an alternate delimiter.

Amarghosh Over a year ago

But it seems he forgot to remove / from the OP's regex before adding the new delimiter #

Ben James Over a year ago

I have edited this and removed the leading and trailing /. I wasn't sure if these were supposed to be part of the pattern, or the delimiters

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