PHP performance

Any recommendations on how to make PHP run faster? I have a script pulling a lot of data from MySQL and generating reports and spitting out data (flush) as it's processing so I can see what's going on. It was taking around 10 seconds to process each order. I reduced the total number of orders being processed. I expected the script to take less time because there were fewer orders to process, but I was surprised to discover that time spent processing each order also reduced almost in half. I figured PHP's memory limit per script at 8mb might be the bottleneck, so I upped it to 128, restarted apache, and reran the script. Increasing available memory had no effect. MySQL is taking most of the cpu while running the script, but I figured I'd make sure to boost PHP as much as possible before going to the MySQL list for MySQL performance tips. Thanks, Ed