autoload - Do PHP opcode cache work with __autoload?

Question

Sorry if this is basic, I am trying to learn as much as I can about OO in PHP and I am slowly learning how to use it (very limited).

So I am wanting to know if __autoload() has any affect on PHP opcode cache's?

Answer 1

Opcode caches work (or at least should work) with autoloading but you can potentially take a performance hit from.

From Remember: be nice to byte code caches:

<arnaud_> does autoload have a performance impact when using apc ?
<Rasmus_> it is slow both with and without apc
<Rasmus_> but yes, moreso with apc because anything that is autoloaded is pushed down into the executor
<Rasmus_> so nothing can be cached
<Rasmus_> the script itself is cached of course, but no functions or classes
<Rasmus_> Well, there is no way around that
<Rasmus_> autoload is runtime dependent
<Rasmus_> we have no idea if any autoloaded class should be loaded until the script is executed
<Rasmus_> top-level clean deps would speed things up a lot
<Rasmus_> it's not just autoload
<Rasmus_> it is any sort of class or function declaration that depends on some runtime context
<Rasmus_> if(cond) function foo...
<Rasmus_> if(cond) include file
<Rasmus_> where file has functions and classes 
<Rasmus_> or heaven forbid: function foo() { class bar { } }

and this mail from Ramus:

To clarify, of course conditionally included files get compiled and cached. The issue is not the included files but the resulting conditionally defined classes and functions needing to be redefined on every request. Whether that is significant or not comes down to the specifics of the situation, but there is no doubt that it is slower. It comes down to a NOP vs. a FETCH_CLASS, for example and the NOP is obviously way faster.