--TEST-- Test array_map() function : usage variations - array with references --FILE-- 0, 1 => &$value4, 2 => &$value2, 3 => "hello", 4 => &$value3, $value4 => &$value2 ); echo "-- with one array --\n"; var_dump( array_map('callback1', $arr1) ); echo "-- with two arrays --\n"; var_dump( array_map('callback_cat', $arr1, $arr1) ); echo "Done"; ?> --EXPECTF-- *** Testing array_map() : array with references for 'arr1' argument *** -- with one array -- array(6) { [0]=> int(0) [1]=> string(5) "hello" [2]=> string(5) "hello" [3]=> string(5) "hello" [4]=> int(0) ["hello"]=> string(5) "hello" } -- with two arrays -- array(6) { [0]=> string(2) "00" [1]=> string(10) "hellohello" [2]=> string(10) "hellohello" [3]=> string(10) "hellohello" [4]=> string(2) "00" [5]=> string(10) "hellohello" } Done