PHP foreach() with arrays within arrays?

I want to call a function on each element in an array. This is obviously very easy with a foreach(), but where I start breaking down is when arrays contain arrays. Can someone help me out with a function that will execute some code for every key -> value pair from a set of arrays within arrays. The depth could, in theory, be infinite, but a good limit would be 3 iterations (array in array in array) if recursion couldn't work.

An example array would be one taken from $_POST below:

Array
(
    [languages] => Array
    (
        [0] => php
        [1] => mysql
        [2] => inglip
    )

    [rates] => Array
    (
        [incall] => Array
        (
            [1hr] => 10
        )

        [outcall] => Array
        (
            [1hr] => 10
        )

    )
)

Just to make sure, what I want to do is run a piece of code (a function) that is passed every 'end node' in the array structure, so in the example above, it would be called when...

[0] => php
[1] => mysql
[2] => inglip
[1hr] => 10
[1hr] => 10

... is found.

Thanks for any help,

James