Php Validate credit card number using regex

function validateCreditCard($cc_number) {
  // regex for credit card number
  $regex = '/^[0-9]{13,16}$/';
  // check if the credit card number matches the regex
  if (preg_match($regex, $cc_number)) {
    // return true if it matches
    return true;
  } else {
    // return false if it doesn't match
    return false;
  }
}

//example
$result = validateCreditCard('1234567890123456');

//output
echo $result; //true