It is good practice to initialize all php variables and arrays. Until now there was no simple way of doing so. There is a 2003 solution by Amit Arora of digitalamit.com but which relies on GLOBAL variables which is not only a bad idea but supposedly GLOBALS will be deprecated in php version 6. My thanks to Amit for the inspiration!
The core problem is that variables cannot be called by reference. But arrays can and THAT is at the heart of the solution!