What is the MM/DD/YYYY regular expression and how do I use it in php?

Question

I found the regular expression for MM/DD/YYYY at http://www.regular-expressions.info/regexbuddy/datemmddyyyy.html but I don't think I am using it correctly.

Here's my code:

$date_regex = '(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)\d\d';  $test_date = '03/22/2010'; if(preg_match($date_regex, $test_date)) {   echo 'this date is formatted correctly';   } else {   echo 'this date is not formatted correctly';   } 

When I run this, it still echoes 'this date is not formatted correctly', when it should be saying the opposite. How do I set this regular expression up in php?

Answer 1

The problem is one of delimeters and escaped characters (as others have mentioned). This will work:

$date_regex = '/(0[1-9]|1[012])[- \/.](0[1-9]|[12][0-9]|3[01])[- \/.](19|20)\d\d/';  $test_date = '03/22/2010'; if(preg_match($date_regex, $test_date)) {   echo 'this date is formatted correctly'; } else {   echo 'this date is not formatted correctly'; } 

Note that I added a forward-slash to the beginning and ending of the expression and escapped (with a back-slash) the forward-slashes in the pattern.

To take it one step further, this pattern won't properly extract the year... just the century. You'd need to change it to /(0[1-9]|1[012])[- \/.](0[1-9]|[12][0-9]|3[01])[- \/.]((?:19|20)\d\d)/ and (as Jan pointed out below) if you want to make sure the whole string matches (instead of some subset) you'll want to go with something more like /^(0[1-9]|1[012])[- \/.](0[1-9]|[12][0-9]|3[01])[- \/.]((?:19|20)\d\d)$/.

---

As others have mentioned, strtotime() might be a better option if you're just trying to get the date out. It can parse almost any commonly used format and it will give you a unix timestamp. You can use it like this:

$test_date = '03/22/2010';  // get the unix timestamp for the date $timestamp = strtorime($test_date);  // now you can get the date fields back out with one of the normal date/time functions. example: $date_array = getdate($timestamp); echo 'the month is: ' . $date_array['month'];     

Answer 2

Regex of the author of the question is almost correct. Date is not validated because a pattern should be:

  pattern="^(0[1-9]|1[012])[/](0[1-9]|[12][0-9]|3[01])[/](19|20)\d\d$" 

or if to be fancy:

  pattern="^(0[1-9]|1[012])[- /.](0[1-9]|[12][0-9]|3[01])[- /.](19|20)\d\d$" 

Please note that this pattern checks only for a format of a date and max/min values for individual date elements. That means a user's entry should be checked for validity of date in JavaScript function and/or a Server (e.g February 29 should not be allowed if a year is not a leap one).

As a side note, if you would like to allow a single digit (let's say for a month), change a month part to

([0-9]|0[1-9]|1[012]) 

Explanation:
[0-9] - single digit between 0 and 9
or
0[1-9] - two digits between 01 and 09
or
1[012] - two digits limited to 10, 11, 12