Toon Verwerft has a post on his site with details about a micro-optimization you can use in your PHP application by using fully-qualified function calls, specifying the namespace even for root level PHP functions.

Today, a little conversation on Twitter escalated rather quickly. Apparently PHP runs function calls differently depending on namespaced or non namespaced context. When calling functions in a namespaced context, additional actions are triggered in PHP which result in slower execution. In this article, I'll explain what happens and how you can speed up your application.

The conversation started with [this tweet]. To understand the difference between global and namespaced function calls better, I'll explain what is going on under the hood.

He starts with this "under the hood" functionality, showing an example of a user-defined, root level function and the opcodes that result. He compares this to the opcodes generated when a namespaced function is called and the extra checking that goes into it (including checking both the namespace and the root levels). Another tweet implied that, because of this difference in checking, fully-qualified function calls would result in a performance increase. He set out to prove it as fact and used the phpbench tool to run four tests with various namespaced and non-namespaced examples. He includes the code he used for the testing and the results from a sample execution. There is, in fact, a slight performance gain from the fully-qualified version. He finishes up the post with some suggestions on using this knowledge including the root-level namespacing for built-in PHP functions.