I am trying to sum the values of two associative arrays. This is the first array:

```
Array
(
[Jan 01, 2013] => Array
(
[COM] => 100
[RES] => 200
)
[Oct 28, 2014] => Array
(
[COM] => 300
[RES] => 400
)
)
```

and this is the second array:

```
Array
(
[Jan 01, 2013] => Array
(
[COM] => 10
[RES] => 20
)
[Oct 28, 2014] => Array
(
[COM] => 30
[RES] => 40
)
)
```

I need to sum the values from these two arrays so that it produces this result:

```
Array
(
[Jan 01, 2013] => Array
(
[COM] => 110
[RES] => 220
)
[Oct 28, 2014] => Array
(
[COM] => 330
[RES] => 440
)
)
```

I found this tutorial to sum values of associative arrays, but it does not seem to work with my multi-dimensional arrays. Any suggestions how to accomplish this? Thank you.