On the Acquia blog they've posted another in their guest post series, this time from Richard Miller, a Senior Technical Consultant with SensioLabs (the people behind the Symfony framework). In this new post he talks about how the performance of PHP is getting better and why.

PHP is not the fastest language in which we could write web applications, yet we continue to do so for many other reasons. Pure speed of a language is rarely the main deciding factor for many projects. [...] So why worry about the speed of the language at all? Well, application architecture is improving and we are finding ways to avoid all those other bottlenecks. [...] Trying to gain speed through profiling and optimising code can be a long and tedious process. Thankfully, improvements in the speed of the language itself give us an improvement in these other areas for free.

He looks at "a brief history" of the language and the major milestones that have lead to the biggest performance gains over the years. He also talks about some of the alternatives out there to "normal PHP" for execution including the HHVM and HippyVM projects. He ends the post with a warning, though - be careful of fragmentation and separation of the community based on these different tools and embrace things like the language specification to keep things on an even keel.