On the PHPixie site there's a new post comparing the overall performance of autoloading versus a single-file approach when it comes to getting the best for your application. They point to the Fat-free Framework as an example of the single file approach.
Thinking about ways of further improving PHPixie I started looking at other projects for inspiration. For example the Fat-Free framework boasts on being contained in a single file. This got me thinking about making a tool for merging all project classes together with vendor libraries into a single for performance boost. MAking such a tool is a fairly trivial task, but still I wanted to be sure it would actually be useful, so I decided to benchmark autoloading classes with composer vs combining them into a single file.
The test script for the benchmarking is included in the post as well as the results from their test runs. In some the XCache extension was used to cache the opcodes, showing a noticeable change from the single-file approach. There's also a measurement of an average framework (autoloaded) request versus the all-in-one method with slightly surprising results. The post also ends with a recommendation for the Composer users out there - using the optional flag to generate a classmap to (slightly) help with autoloading speed.