php regular expression for mm-dd-yy

opioid · 03-15-2005, 12:56 PM

Hey folks, I'm learning regular expressions and I have a question for you regarding how to validate server-side dates like MM-DD-YY.

Can someone give me an example of the regular expression I could match my string against? I have read several pages on this but I'm not seeing how they breakdown.

Thank you!
-O

Matir · 03-15-2005, 01:03 PM

A regular expression could only match the format, not the ability to make sure they don't put in 02-31-05 or something.

But this should be functional to match the format:

/[0-9]{1,2}\-[0-9]{1,2}\-[0-9][0-9]/

opioid · 03-15-2005, 01:33 PM

Actually, I already have this:

^[0-9]{2}-[0-9]{2}-[0-9]{2}$

What's the difference?

Thanks,
O

keefaz · 03-15-2005, 02:17 PM

Your expression means it require 2 digits number to validate, with the one
above yours, one digit and 2 digits numbers match

example :
01-01-05 <-- match
1-1-05 <-- does not match

Matir · 03-15-2005, 04:31 PM

I am not sure if the \ in front of the - in mine is required or not: the - indicates a range within [], but it's probably not required. So I think this is preferred:
/[0-9]{1,2}-[0-9]{1,2}-[0-9]{2}/
If you want to permit 4 digit years (OPTIONALLY), try this:
/[0-9]{1,2}-[0-9]{1,2}-([0-9]{2})?[0-9]{2}/

(I believe that requires extended regular expression matching for the ?)

opioid · 03-17-2005, 12:36 PM

Tight! Thanks keefaz and Matir!

TheLinuxDuck · 03-17-2005, 02:34 PM

Three things:

1. Don't forget word boundaries. Wrap the regex in \b \b, otherwise, you could match a:
222-02-02
2. Don't forget that \d is the same as [0-9]. This will shorten the regexp, and make it less sloppy (if that can be said about a regexp).
3. Instead of saying "[0-9]{1,2}", you could shorten the regexp by saying "\d?\d". That's half the length for one segment. (=

Matir · 03-17-2005, 03:22 PM

I'm not sure all implementations of regexp engines support \b and \d. I may be wrong though (not that uncommon actually). My regular expression is also a bit easier to read (if that can be said for a regexp).