--TEST-- Test array_merge() function : usage variations - Mixed keys --FILE-- 'twenty', 'thirty' => 30, true => 'bool'); $arr2 = array(0, 1, 2, null => 'null', 1.234E-10 => 'float'); var_dump(array_merge($arr1, $arr2)); var_dump(array_merge($arr2, $arr1)); echo "Done"; ?> --EXPECTF-- *** Testing array_merge() : usage variations *** array(8) { [0]=> string(4) "zero" [1]=> string(6) "twenty" ["thirty"]=> int(30) [2]=> string(4) "bool" [3]=> string(5) "float" [4]=> int(1) [5]=> int(2) [""]=> string(4) "null" } array(8) { [0]=> string(5) "float" [1]=> int(1) [2]=> int(2) [""]=> string(4) "null" [3]=> string(4) "zero" [4]=> string(6) "twenty" ["thirty"]=> int(30) [5]=> string(4) "bool" } Done