public function testKDiffAcceptsClosure()
 {
     $xao = new XArray(['x' => 1, 'ab' => 2, 'z' => 3]);
     $obj = $xao->kdiff(['x' => 4], function ($a, $b) {
         return length_compare_func($a, $b);
     });
     $this->assertEquals(['ab' => 2], (array) $obj);
 }
 public static function static_length_compare($a, $b)
 {
     return length_compare_func($a, $b);
 }
 public function testXKIntersectAcceptsClosure()
 {
     $xao = new XArray(['x' => 1, 'ab' => 2, 'z' => 3]);
     $obj = $xao->xkintersect(['a' => 4, 'abc' => 'xyz'], function ($a, $b) {
         return length_compare_func($a, $b);
     });
     $this->assertEquals(['a' => 4], (array) $obj);
 }