array(4) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
  [3]=>
  string(1) "d"
}
array(4) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
  [3]=>
  string(1) "d"
}
array(4) {
  [2]=>
  string(1) "a"
  [4]=>
  string(1) "b"
  [6]=>
  string(1) "c"
  [7]=>
  string(1) "d"
}
array(4) {
  [-2]=>
  string(1) "a"
  [-4]=>
  string(1) "b"
  [-6]=>
  string(1) "c"
  [0]=>
  string(1) "d"
}
array(2) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
}