Manuel João Silva

The fastest and the correct way to get the last key from an array is:

$lastkey = array_pop(array_keys($arr));

Example:

$arr[] = array("red" => "apple", "yellow" => "banana");

Let’s say you want to add another element to the previous created array, for that you need to know the last created index so:

$lastkey = array_pop(array_keys($arr));
$arr[$lastkey]["brown"] = "kiwi";

And there you have it.