array_merge() no longer accepts non-array parameters to merge. 

<?php
    $scandinavia = array('Denmark', 'Norway', 'Finland');
    $uk = "The UK";

    $europe = array_merge($scandinavia, $uk);

    print_r($europe);
?>


PHP 4:

Array
(
    [0] => Denmark
    [1] => Norway
    [2] => Finland
    [3] => The UK
)


PHP 5:

Warning: array_merge(): Argument #2 is not an array in - on line 7