This document discusses various topics related to PHP internals and performance optimization. It explains that PHP code is compiled at runtime into opcodes that are then executed. It describes profiling tools like XHProf that can analyze runtime performance. It also discusses opcode caching with extensions like APC that improve performance by caching compiled code. Finally, it cautions developers to be aware of how language features like traits actually work at the compiler level and can introduce unintended coupling.

1. PHP under the hood
Frank Neff

2. PHP

3. is

4. compiled

5. at

6. runtime!

7. Source code you write...

8. …OpCodes you run

9. Kidding me?

10. Looks confusing, but this is...
● how PHP works
● cool for debugging purposes
● visualizing code complexity
● helpful trying to understand opcaches like
APC

11. Try it with your code
http://explain.php.net.so

12. So this is about profiling?

13. No! XHProf is about profiling
● XHProf is a function-level hierarchical
profiler for PHP
● Reports timing information for every function
called
● C-Extension can be loaded via PECL
● GUI and libs available

14. Looks like this

15. Try it with your code
http://xhprof.io/

17. Compiling at runtime is slow!

18. OpCode Cache
● Performance enhancing extension for PHP
● Hooking into the execution life-cycle
● Caching the results of the compilation phase
for later reuse
● APC
● XCache

19. HHVM
● HipHop Virtual Machine
● Designed for executing PHP programs
● Predecessor HPHPc makes C out of PHP
● Uses a just-in-time (JIT) compilation
● http://www.hhvm.com/

21. LetsTalkAboutNamespaces

23. Kidding me?

24. No!
● Namespaces in PHP are just class-prefixes
● They are added to each classname by the
compiler
● The result is called a FQCN - Fully Qualified
Class Name

28. What do you think of copy &
paste code?

30. What do you think of traits?

32. Cool. Traits are for...
● Code reusage
● Multiple inheritance
● Keeping stuff you often use in different
contexts
● No need for complex OOP architectures

33. Nooooooo!

34. Seriously...

35. No.

36. No. Because traits are...
● Copied into every single class at compile-
time
● Therefore not runtime bindable
● Not testable
● Tightly coupled
● Make it easier to cross SRP (one god-class)

37. (traits === copy & paste)

38. Wanna read more?
● PHP at the Core: A Hacker's Guide
● PHP Compiler Internals
● PHP OpCodes
● PHP Internals
● Are Traits The New Eval?
● PHP-RFC’s

39. So you’re telling me not to use
such cool features in PHP?

40. No.
Just be aware of how
things work in PHP
while writing code

42. Frank Neff
Software Engineer
Thanks
http://stickerish.com/
http://xhprof.io/
http://www.vbulletin.com/
http://en.wikipedia.org/
http://blog.supermedia.com/
http://twitter.com/
http://tossfair.wordpress.com/
http://juliannb4.deviantart.com/
http://www.walldime.com/
http://gist.github.com
http://meanduchicago.wordpress.com/
Images ● @frank_neff
● github.com/frne
● speakerdeck.com/frne
● frankneff.ch
● ymc.ch