Original
object(test)#1 (2) {
  ["b"]=>
  array(2) {
    [0]=>
    int(3)
    [1]=>
    int(4)
  }
  ["a"]=>
  array(2) {
    [0]=>
    int(1)
    [1]=>
    int(2)
  }
}
Clone
object(test)#2 (2) {
  ["b"]=>
  array(2) {
    [0]=>
    int(3)
    [1]=>
    int(4)
  }
  ["a"]=>
  array(2) {
    [0]=>
    int(1)
    [1]=>
    int(2)
  }
}
Modify
object(test)#2 (2) {
  ["b"]=>
  int(6)
  ["a"]=>
  int(5)
}
Done