Migrating from PHP 5.2.x to PHP 5.3.x
PHP Manual

Backward Incompatible Changes

Although most existing PHP 5 code should work without changes, please take note of some backward incompatible changes:

The following keywords are now reserved and may not be used in function, class, etc. names.


Migrating from PHP 5.2.x to PHP 5.3.x
PHP Manual