public function digital($subject) : bool
    {
        if (is_int($subject)) {
            return true;
        }
        if (!is_string($subject)) {
            return false;
        }
        // Yes, ctype_... returns fals on ''.
        return ctype_digit('' . $subject);
    }
public function digital($subject) : bool
    {
        if (is_int($subject)) {
            return true;
        }
        if (!is_string($subject)) {
            return false;
        }
        // Yes, ctype_... returns fals on ''.
        return ctype_digit('' . $subject);
    }
public function digital ( $ subject ) : bool { if ( is_int ( $ subject ) ) { return true ; } if ( ! is_string ( $ subject ) ) { return false ; } // Yes, ctype_... returns fals on ''. return ctype_digit ( '' . $ subject ) ; }
Non-negative integer or stringed integer.

If negative integer should pass, use numeric()
and then check it's return value.

@see Validate::integer()

@see Validate::bit32()
@see Validate::bit64()
@see Validate::positive()
@see Validate::negative()
@see Validate::nonNegative()
@see Validate::min()
@see Validate::max()
@see Validate::range()

@param mixed $subject
Checked stringified.

@return bool
Non - negative integer or stringed integer .