--TEST-- Test array_diff_key() function : usage variation - Passing boolean indexed array --FILE-- '0', 1 => '1', -10 => '-10', 'true' => 1, 'false' => 0); $boolean_indx_array = array(true => 'boolt', false => 'boolf', TRUE => 'boolT', FALSE => 'boolF'); echo "\n-- Testing array_diff_key() function with boolean indexed array --\n"; // loop through each element of the array for arr1 var_dump( array_diff_key($input_array, $boolean_indx_array) ); var_dump( array_diff_key($boolean_indx_array, $input_array) ); ?> ===DONE=== --EXPECTF-- *** Testing array_diff_key() : usage variation *** -- Testing array_diff_key() function with boolean indexed array -- array(3) { [-10]=> string(3) "-10" ["true"]=> int(1) ["false"]=> int(0) } array(0) { } ===DONE===