Evert Pot has a quick post showing how you can make your code fork MySQL connections for better performance.

For some of our long-running processes we use PHP. It makes total sense from our perspective, because we can re-use all our existing business logic from our main PHP web application. To make things more efficient, I recently started some work on using forks and have a couple of worker processes around.

His sample script makes use of the pcntl_fork and pcntl_wait functions in PHP to spawn off processes that will be closed off when no longer needed.