Is there some guide out there that describes how the PHP internals?
- How files are loaded (required, included)?
- How they are parsed and executed?
- How memory is allocated?
- How objects are created/destroyed?
- How external modules are loaded?
- How the stack/heap works?
- How opcode caching actually work?
- Common hacks and performance tips?
Sounds to me like you’re you should look for resources on PHP Internal development. Looking for this information elsewhere will be really scattered.
I suggest picking up a PHP Core development book from your local book store and giving it a read. PHP.net has an underdeveloped beginners reference if you wanted to start there.