Disclaimer: PHP core dev.

Be careful with microbenchmarks. From my experience, there tends to be very little correlation between performance improvements on microbenchmarks and real applications. If you improve performance on the microbench suite by a factor of two, you definitely will not get a factor of two on real applications -- more likely, it will be something like 2%.

Basically, if the benchmark is not testing end-to-end performance on Wordpress (or similar), then it's a useless benchmark.