PHP DD/MM/YYYY Validation [duplicate] - php

Question

This question already has answers here:
My pattern isn't matching a ISO style date, why? [duplicate]
(3 answers)
Closed 7 years ago.
apologies for probably a simple question, but i am new to PHP and Javascript.
I am creating a login validation in PHP that requires a registering user to input their date of birth in a DD/MM/YYYY Format, that returns an error message if the date is entered in any other format. I am unsure how to do this, other than using preg_match, however this doesnt seem to work...
variables:
$DOB = $_POST['DOB'];
$error_message = '';
The Date Validation Segment
elseif (!preg_match("/^(0?[1-9]|[12][0-9]|3[01])\/\.- \/\.- \d{2}$/", $DOB))
{
$error_message = 'Invalid Date';
}
Error Display
if ($error_message != '')
{
echo 'Error: '.$error_message.' Go Back.';
echo '</body> </html>';
exit;
}
else
{
echo'<p><strong>Form Submitted Successfully!</strong></p>';
}
This is not a duplicate, i tried other threads and none of their solutions worked.

Answer 1

You should use more than a regular expression. For example, you should not allow something like 31/02/2015, because there's no 31th in February!
I have a function that works well:
function isDate($string) {
$matches = array();
$pattern = '/^([0-9]{1,2})\\/([0-9]{1,2})\\/([0-9]{4})$/';
if (!preg_match($pattern, $string, $matches)) return false;
if (!checkdate($matches[2], $matches[1], $matches[3])) return false;
return true;
}
It first uses preg_match to check for the formal validity of DD/MM/YYYY, grabbing DD, MM and YYYY portions into the $matches array. Then it check the validity of the date itself using the built-in PHP function checkdate.
You can use that in your code like:
if (!isDate($DOB)) {
$error_message = 'Invalid Date';
}

Answer 2

string_explode given string and then pass parts of it to
bool checkdate ( int $month , int $day , int $year )
unfortunately you cannot know if user posted month and day in your format if day is not greater than 12

Answer 3

You can do it like this in PHP:
$date=explode("/",$_POST['DOB']);
if(checkdate ($date[1] ,$date[0] ,$date[2]))
{
echo "valid";
}
else
{
echo "invalid";
}
checkdate will only return true if the three value behind "/" is valid, so if there's no "/" its invalid, same as they put numbers in wrong order.
check manual http://php.net/manual/en/function.checkdate.php