How do I use array_unique on an array of arrays?

问题

I have an array

Array(
[0] => Array
    (
        [0] => 33
        [user_id] => 33
        [1] => 3
        [frame_id] => 3
    )

[1] => Array
    (
        [0] => 33
        [user_id] => 33
        [1] => 3
        [frame_id] => 3
    )

[2] => Array
    (
        [0] => 33
        [user_id] => 33
        [1] => 8
        [frame_id] => 8
    )

[3] => Array
    (
        [0] => 33
        [user_id] => 33
        [1] => 3
        [frame_id] => 3
    )

[4] => Array
    (
        [0] => 33
        [user_id] => 33
        [1] => 3
        [frame_id] => 3
    )

)

As you can see key 0 is the same as 1, 3 and 4. And key 2 is different from them all.

When running the array_unique function on them, the only left is

Array (
[0] => Array
    (
        [0] => 33
        [user_id] => 33
        [1] => 3
        [frame_id] => 3
    )
)

Any ideas why array_unique isn\'t working as expected?

来源：https://stackoverflow.com/questions/2561248/how-do-i-use-array-unique-on-an-array-of-arrays