Have you tried using regular expressions?
//check the first section is singular or multi, check area code between 0 and 9, check any additional integers
$pattern = "[0|00]+[0-9]+[^\\s]";
$phone_number = "000263712702879"; //international phone number
if(preg_match($pattern, $phone_number)) {
echo "this is a number";
} else echo "this not a number";