array insert php funciton (insert indexed or associative array into another)

array_insert.php

<?php

/**
 * @param array          $array
 * @param string|integer $position numeric key
 * @param array          $insert_array
 * @param string         $at
 */
function array_insert(array &$array, $position, array $insert_array, $at = 'after')
{
    if (!ctype_digit($position)) {
        $position = array_search($position, array_keys($array));
        if (false === $position) {
            $array = $insert_array + $array;

            return;
        } else {
            if ($at == 'after') {
                $position++;
            }
        }
    }

    $first_array = array_splice($array, 0, $position);
    $array = array_merge($first_array, $insert_array, $array);
}