PHP says “Nooo” to my integer

Another eye-opener from PHP is the unexpected behaviour of integer filters. Here is a test case class checking “01” and “10” whether they are integers or not.

class TestFilters extends PHPUnit_Framework_TestCase
{

    public function test_filter_int_with_zero_prefix ()
    {
        $result = filter_var('01', FILTER_VALIDATE_INT) !== false;
        
        $this->assertTrue($result);
    }
    
    public function test_filter_int_with_zero_suffix ()
    {
        $result = filter_var('10', FILTER_VALIDATE_INT) !== false;
        
        $this->assertTrue($result);
    }
    
}

Refer to: http://php.net/manual/en/filter.filters.validate.php