Date validation Unknown modifier error

I'm using this string to validate a date field in dd/mm/yyyy' and 'dd-mm-yyyy format:

'/^(0?[1-9]|[12][0-9]|3[01])[\/\.- ](0?[1-9]|1[0-2])[\/\.- ](19|20)\d{2}$/'

but I get this error

Warning: preg_match() [function.preg-match]: Unknown modifier '\' i开发者_开发百科n /var/www/...fields_lib.php on line 102

Keep in mind the the above string is entered on a web application optional validation form field without any delimeter, because I think the form embed the delimeters itself. For other validation types like, integer and decimal numbers, I had to remove the delimeters for the validation to work on this specific form.

Any ideas ?

Thank You

---

You don't need the backslashes in character classes, so your regex should read (in part) [/. -]. Also note that the space and the dash have switched spaces, because [.- ] would be interpreted as "any character between . and .

---

I don't get that error; instead I get a "range out of order" error, for the reason @CanSpice gave. To get the other error, I have to remove the first backslash in the character class ([/\.- ] instead of [\/\.- ]). Then it interprets the / as a regex delimiter, and it expects the next character to be a modifier (like i for case-insensitive, or m for multiline).

So you've got two problems: the - being treated as a range operator, and the / being treated as a regex delimiter. You can deal with both problems by escaping the offending characters with backslashes (i.e., [\/.\- ]), but each problem has a more elegant solution. If you move the - to the first or last position where it couldn't form a range, it gets treated as a literal -. As for the /, you can use something else for the regex delimiter. For example:

'~^(0?[1-9]|[12][0-9]|3[01])[/. -](0?[1-9]|1[0-2])[/. -](19|20)\d{2}$~'

FYI, the . never needed to be escaped at all. In character classes, most regex metacharacters lose their special meanings. You just happened to run afoul of two special cases. :-/