A crude array_splice that preserves keys.

array_splice.php

<?php 
function array_splice_preserve ($input, $offset, $length, $replacement) {
    $keys = array_keys($input);
    $values = array_values($input);
    array_splice($keys, $offset, $length, array_keys($replacement));
    array_splice($values, $offset, $length, array_values($replacement));
    return array_combine($keys, $values);
};