Verifying date format in PHP

There are several ways to check the format of a date in PHP; the simplest method is to make use regular expressions.

To confirm a date format DD/MM/YYYY, where the days and/or month can be given as single number:

<?php
	function testDate( $value )
	{
		return preg_match( '`^\d{1,2}/\d{1,2}/\d{4}$`' , $value ) )
	}
	
	testDate( '21/11/1999' ); // -> true
	testDate( '3/9/2008' ); // -> true

	testDate( 'a/04/2003' ); // -> false
	testDate( '28-01-2000' ); // -> false

	testDate( '99/13/1978' ); // -> true
?>

Note that:
As the last call, this function does not check the validity of the date itself but only the validity of its format.