Reference counting is one of the hottest new features in PHP 4. It reduces the memory consumption of your PHP applications, improves performance, and provides you with some sophisticated programming tools. To get the most out of this new PHP 4 feature, it's important to understand exactly how it works and how it differs from PHP 3. Topics include: Data values in PHP 3, What is reference counting, Advantages of reference counting, Reference counting in PHP 4, Aliasing: added language flexibility in PHP 4, and How will reference counting effect you?.