I have a string like '6554', and I would like to change this to an array, resembling the following:

```
Array([0] => 6, [1] => 5, [2] => 5, [3] => 4)

```

The problem is that I can not be certain of the length of the number and the number has nothing separating each digit. The number will not be negative or a float. Any ideas on how I could do this?