1:
$apple contains array(2) {
  ["foo"]=>
  string(3) "bar"
  ["bar"]=>
  string(3) "foo"
}

2:
$orange contains array(2) {
  ["foo"]=>
  string(3) "bar"
  ["bar"]=>
  string(3) "foo"
}

3:
$pluto contains array(2) {
  [1]=>
  string(1) "d"
  [0]=>
  int(34)
}

4:
$pippo contains array(4) {
  ["foo"]=>
  string(3) "bar"
  ["bar"]=>
  string(3) "foo"
  [100]=>
  int(-100)
  [-100]=>
  int(100)
}

5:
$paperino contains array(5) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [6]=>
  string(1) "c"
  [4]=>
  string(1) "d"
  [7]=>
  string(1) "e"
}

5:
$strange_multiarray contains array(3) {
  ["foo"]=>
  string(3) "bar"
  [42]=>
  int(24)
  ["multi"]=>
  array(1) {
    ["dimensional"]=>
    array(1) {
      ["array"]=>
      string(3) "foo"
    }
  }
}

and each element of the array $strange_multiarray can be accessed with the 'array[key]' syntax expression.
string(3) "bar"
int(24)
array(1) {
  ["dimensional"]=>
  array(1) {
    ["array"]=>
    string(3) "foo"
  }
}
array(1) {
  ["array"]=>
  string(3) "foo"
}
string(3) "foo"