Slawek Lukasiewicz's Blog: PHP application diagnostics - Memtrack
Application profiling can help us determine bottlenecks and possible problems during development. But sometimes we also need to diagnose problems in production environment. Frequent performance problems are connected with functions and methods using too much memory.
The tool allows you to set up thresholds for memory consumption and, if the scripts exceeds it, add warnings to your log files. He includes the simple instructions to install it (via PECL) and enable it in your php.ini. Some sample code to create a memory overvload is included to test it out. Configuration options let you set the limits and define functions to ignore if you know for sure there's trouble spots.