PHP Myth: static function call faster than instance function call

There exist a reasonable number of myths about PHP. One I will challenge today. If you ask an average PHP programmer whether a static function call or a function call on an instance performs better he or she will problably say - without thinking - static. This is wrong.

Sure, if you want to call a method on an instance you first have to instantiate that instance. This takes some time by its own. The sum of CPU time for instantiation and a single method call is in fact greater than the CPU time needed to call a static function. So, if you ask for the time of single calls you will support the myth. But the question is wrong.

In real life you will never do isolated calls. The question of interest is not how a single call performs but how the different kinds of method calls scale. If you measure this you will get a different picture. The instance calls scale definitely better. If you even have just a handful of static method calls on a class the same calls on an instance - a singleton for example - will save you time.

The image below shows a measurement with empty methods and light weight classes on PHP 5.2.5. The point where the two lines are crossing may vary with the complexity of your class.