array(2) {
  [0]=>
  string(2) "a1"
  [1]=>
  string(2) "a2"
}
array(2) {
  [0]=>
  string(2) "a1"
  [1]=>
  &string(2) "a2"
}
array(2) {
  [0]=>
  string(2) "a1"
  [1]=>
  &string(2) "b3"
}