PHP Compiled Variables Explained

Sara Golemon, one of the most famous writers of PHP books, gave an explanation of the compiled variables in PHP.  This is an important optimization of PHP interpreters and was missing in PHP 5.0 (Zend Engine 2.0) but introduced in PHP 5.1 (Zend Engine 2.1).

• Sala Colemon, Compiled Variables, May 24, 2006
  

It is very concise but has enough information to understand the new optimization in PHP.