v: 0
v: 1
v: Array
v: 4
array(4) {
  [0]=>
  string(1) "v"
  [1]=>
  string(1) "v"
  [2]=>
  string(1) "v"
  [3]=>
  &string(1) "v"
}
k: 0, v: 0
k: 1, v: 1
k: 2, v: Array
k: 3, v: 4
array(4) {
  [0]=>
  string(1) "v"
  [1]=>
  string(1) "v"
  [2]=>
  string(1) "v"
  [3]=>
  &string(1) "v"
}