Is a local PHP include() file cached?

Question

After doing some research i'm struggling to find a definitive answer on how and if a PHP include() file is cached.

The closest i've found is here but it doesn't quite make sense to me.

I have several methods that use other methods from different files and I want to avoid placing include()'s just at the top of the file but i'm not sure how this might affect performance.

Any help is appreciated.

Answer 1

PHP is an interpreted language. The default PHP runtime compiles PHP sourcecode to an intermediate representation called PHP bytecode which is then executed. A bytecode cache stores this compiled representation of PHP sourcecode in shared memory. This eliminates the need to load and compile sourcecode on each request which leads to a significant increase in performance (up to 70% more requests per second).

The basic idea, when executing a PHP script is in two steps:

• First: the PHP code, written in plain-text, is compiled to opcodes
• Then: those opcodes are executed . When you have one PHP script, as long as it is not modified, the opcodes will always be the same ; so, doing the compilation phase each time that script is to be executed is kind of a waste of CPU-time.

To prevent that redundant-compilation, there are some opcode caching mechanism that you can use.

Once the PHP script has been compiled to opcodes, those will be kept in RAM -- and directly used from memory the next time the script is to be executed ; preventing the compilation from being done again and again.

Read more

• https://blog.graphiq.com/500x-faster-caching-than-redis-memcache-apc-in-php-hhvm-dcd26e8447ad#.tsokdw9d4
• https://github.com/TerryE/opcache/wiki/The-Zend-Engine-and-opcode-caching#opcode-caching-with-opcache
• https://juokaz.com/blog/from-php-to-machine-code