regular expression date format matching

[snehula]

Hi there,

those regular expressions.. trying to get the hang of it.
I want the user to enter date in the format dd/mm/yyyy.
here is the regular expression that I use to match the date with:

$regexp = '/^(0[1-9]|[12][0-9]|3[01])[\/](0[1-9]|1[012])[\/](19|20[0-9]{2})$/';

I sure can't see what the mistake is but preg_match($regexp, $somedate) keeps returning false (although I got 0 once or twice) for any date that's in the format above (dd/mm/yyyy). So, where is the mistake?

Another thing I'd love to know is, as far as i know the forward slash in the end and beginning is a delimiter. Could i use any other character instead the slash?

[brotherhood of LAN]

Could i use any other character instead the slash?

Yes, I usually use a single quote but the convention does seem to be forward slash (a convention from other languages i think)

$regexp = '/^([0-9]{2}\/){2}(?:19|20)[0-9]{2}$/';

Try that one.

Match 2 numbers and forward slash twice (dd/mm/)

Match 19|20 (yy)

Match 2 Numbers [yy]

That does insist that a 0 is placed for days and months like 01, 02 etc which may not be as intuitive as you'd like for user input.

[g1smd]

[\/]

is garbage.

Don't escape the slashes.

Do choose a different end-point character. It MUST be different to any of the characters in the RegEx pattern.

$regexp = '#^(0[1-9]|[12][0-9]|3[01])/(0[1-9]|1[012])/(19|20[0-9]{2})$#';

[Readie]

Little more friendly... Doesn't insist on a leading 0, and makes sure days can't go above 31:

!^(0?\d|[12]\d|3[01])/(0?\d|1[012])/((?:19|20)\d{2})$!

Also, you made a tiny mistake g1msd:

(19|20[0-9]{2})

Effectively:

19 or 20xx

[g1smd]

Apologies. I got the parentheses in the wrong place, copying and pasting from the OP. My eye was on the other errors.

Use

(19|20)[0-9]{2}

[lucy24]

(0[1-9]|[12][0-9]|3[01])/

In something this short, saying

(0?[1-9]|[12][0-9]|3[01])/

shouldn't place an undue burden on your computer. Or you can do an on-the-fly rewrite of
([1-9])/ to 0$1/
That's assuming you take the radical position of making the computer subordinate to the human ;)

Is there a problem with \d instead of [0-9] ?

Oh, and will it be routed via something that filters out spurious dates like 31/04 ? Or 29/02 in years that didn't have one? (Fortunately 2000 did, so a simple "multiple of 4" function will pick up all of them.) Since you're talking about user input, a dropdown selector for the month might be safer, so you can be sure what "07/11" means. 12 items, as for months, is about the limit on dropdowns; go to 30 or more and it gets annoying.

[g1smd]

Use

\d

if your system uses PCRE RegEx, or

[0-9]

if you want POSIX.