regex - check date formats

Question

I'd like some help please. I'm having am input field where I'd like to check if the user has entered his date of birth in these formats: dd/mm/yyyy or dd-mm-yyyy

if(preg_match('/^[0-9]{2}-[0-9]{2}-[0-9]{4}$/', $_POST['dob'])){
    // ok
} else {
    // there's an error
}

How can I change my regular expression to match either the '/' or '-' between the numbers?

Answer 1

Put the patterns which matches date formats inside a non-capturing group delimited by an alternation operator.

if(preg_match('~^[0-9]{2}(?:-[0-9]{2}-[0-9]{4}|/[0-9]{2}/[0-9]{4})$~', $_POST['dob'])){
    // ok
} else {
    // there's an error
}

OR

Use capturing group and then refer the capturing characters through back-referencing.

if(preg_match('~^[0-9]{2}([-/])[0-9]{2}\1[0-9]{4}$~', $_POST['dob'])){
    // ok
} else {
    // there's an error
}

DEMO 1

DEMO 2