A simple function to recognize whether the value is a natural number.

is_natural.php

<?php
 
function is_natural($val, $acceptzero = false)
{
    $return = ((string) $val === (string) (int) $val);
    if ($acceptzero) {
        $base = 0;
    } else {
        $base = 1;
    }
    if ($return && intval($val) < $base) {
        $return = false;
    }
    return $return;
}