As someone with a bit of experience scaling PHP, it seems to me that the main problem with the language is not its raw performance (which seems on a par with its more cousins Python and Ruby) but rather its single-request model. For every request, mod_php creates a new interpreter, which has to do all the work to set up the framework, auto-loading the required classes, reading additional data every time. What's more, the request has to create a new database connection for every request; the single-request model doesn't allow the use of a database pool. (This doesn't change fundamentally with handlers other than mod_php, such as php-fpm.)

With languages like Python and Ruby, not to mention Java, a single interpreter process or thread can handle many requests and can re-use the database connection. In PHP, you're forced to do all the set-up all over again for every request. This is particularly wasteful with frameworks like Laravel, which do a non-trivial amount of work for setting up the application object, IoC controller.

Am I missing something here? I can't believe companies using PHP on a larger scale, like Facebook, discard and re-create the application environment and all DB connections (!) for every single request.