array_unique() always returns only 1 result for multi-dimentional arrays

Here is the code:

$temp = Array (
	Array('a', 'b'),
	Array('x', 'y'),
); 
print_r($temp); 
print_r(array_unique($temp)); 

Here is the result in PHP 4.0.4, as it should be, i.e. no array change:

Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )

    [1] => Array
        (
            [0] => x
            [1] => y
        )

)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )

    [1] => Array
        (
            [0] => x
            [1] => y
        )

)

Here is the result in PHP 4.0.6:

Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )

    [1] => Array
        (
            [0] => x
            [1] => y
        )

)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
        )

)

I have put the code at http://www.99servers.com/develop/test/array_unique.php, you can see the results by yourself.

My phpinfo() is located at http://www.99servers.com/develop/test/phpinfo.php, just in case you need additional details about my php 4.0.6 configuration.