The example may get u into thinking that the identical operator returns true because the key of apple is a string but that is not the case, cause if a string array key is the standart representation of a integer it's gets a numeral key automaticly.
The identical operator just requires that the keys are in the same order in both arrays:
<?php
$a = array (0 => "apple", 1 => "banana");
$b = array (1 => "banana", 0 => "apple");
var_dump($a === $b); $b = array ("0" => "apple", "1" => "banana");
var_dump($a === $b); ?>