Code tracing with Zend's PHP server
One of the new features in Zend Server 5 reportedly behaves like an airplanes black box: The beta release includes a tracing option that captures the full execution of PHP scripts in real-time.
The feature is designed to help developers find and fix programming flaws by recording the hierarchy of function calls, including submitted arguments and return values. Developers can manually enable the tracing feature, for example, when looking for performance bottlenecks. According to Zend, the Server activates the feature automatically when it encounters a "problem".
Load-intensive applications benefit from a "Job Queue". It allows PHP scripts to be started as batch jobs at a certain time depending on server load and priority. The batch jobs can be executed on the same computer that runs Zend Server or on another computer.
There is a variant for PHP 5.2 and 5.3. and a Windows beta is available free of charge. When queried, the vendor said the free community version will contain neither the tracing nor the Job Queue feature.