Getting Value from third dimension of array

I’m having lots of trouble grasping this. Given the array below, how do I extract and display a list of just the posts id numbers from site_id 26?

Array
(
    [0] => Array
        (
            [site_id] => 1
            [posts] =>
        )
    [1] => Array
        (
            [site_id] => 26
            [posts] => Array
                (
                    [0] => 1441
                    [1] => 1445
                    [2] => 3721
                    [3] => 1449
                    [4] => 1451
                    [5] => 1457
                    [6] => 3832
                    [7] => 1510
                    [8] => 1512
                    [9] => 1534
                    [10] => 1516
                    [11] => 1544
                    [12] => 1542
                )
        )
)

Thanks in advance.