PHP - 组合子数组并按值排序？

This is what i've got now:

这就是我现在所拥有的：

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [id] => 53
                    [date] => 18 Sep 2010 10:29
                    [user] => 52
                    [post] => ytiuy
                )

            [1] => Array
                (
                    [id] => 55
                    [date] => 11 Sep 2010 11:14
                    [user] => 52
                    [post] => this is a test post :]
                )

        )

    [1] => Array
        (
            [0] => Array
                (
                    [id] => 56
                    [date] => 4 Sep 2010 03:19
                    [user] => 55
                    [post] => pppost :DD:D:D:D
                )

        )

)
Arra