php二维数组获取相同键值并输出

Question

现在我有个二维数组
array（

[aaa_0] => Array
    (
        [2] => 2
        [4] => 4
        [5] => 5
    )
[aaa_1] => Array
    (
        [1] => 1
        [2] => 2
        [5] => 5
    )

[aaa_2] => Array
    (
        [5] => 5
    )

）
我怎么样才能取出aaa_0和aaa_1和aaa_2中相同的键值？？即5