php數組指定位置插入不刪除當前key

$arr = array(
    'tt' => 1333,
    'cc' => 333,
    'aaz' => 2333,
    'ee' => 78,
)

/*
 插入一個【 鍵 'bb' 值 123】到tt後邊得 $arr
Array
(
    [tt] => 1333
    [bb] => 123
    [cc] => 333
    [aaz] => 2333
    [ee] => 78
)
*/
        function array_insert (&$array, $position, $insert_array) {
            $first_array = array_splice ($array, 0, $position);
            $array = array_merge ($first_array, $insert_array, $array);
        }


        $arr = array(
            'tt' => 1333,
            'cc' => 333,
            'aaz' => 2333,
            'ee' => 78,
        );
        $temp["bb"] = 33;
        array_insert($arr,1,$temp);
        var_dump($arr);