Remove source code manually disabling magic quotes.
Extending exceptions.
Introduce inc(&$a), incrementSuffix($string) and Stack->create(...).
Major code review for stack implementation. Introduce uniqueId.

* Prefer $this over NULL as return value.
* Use assert statements to ensure preconditions in methods.
* Stack operations should work with arrays as well.
* Introduce Stack::getNormalizedArray()
Introduce Stack::iteratePopping.