eaccelerator

On numerous LAMP servers we run, we repeatedly experienced an odd and disturbing problem. Users were fed some "random" ASCII text, instead of a rendered page, leaving them in complete frustration. After rigorous investigation, we came to a conclusion that the problem lies in a combination of PHP's zlib compression and eAccelerator. The odd part that greatly complicated debugging was that only some users experienced the problem.

eAccelerator is a "free open-source PHP accelerator, optimizer, and dynamic content cache". It's also one of the most widely used and stable implementations. The performance gains from eAccelerator are very imperssive, especially since there is no code-change involved and cache is transparent - data is real-time.

zlib comperssion is a PHP feature that compresses output (pages) and can significantly decrease both traffic usage, as well as page load times.

Unfortunately, the two do not work well together.