PHP APC in CLI mode

php performance optimization command-line-interface apc
Matic picture Matic · Aug 7, 2009 · Viewed 29.3k times · Source

Does APC module in PHP when running in CLI mode support code optimization? For example, when I run a file with php -f <file> will the file be optimized with APC before executing or not? Presuming APC is set to load in config file. Also, will the scripts included with require_once be also optimized?

I know optimization works fine when running in fastcgi mode, but I'm wondering if it also works in CLI.

apc_* functions work, but I'm wondering about the code optimization, which is the main thing I'm after here.

Happy day, Matic

Answer

Pascal MARTIN picture Pascal MARTIN · Aug 7, 2009

The documentation of apc.enable_cli, which control whether APC should be activated in CLI mode, says (quoting) :

Mostly for testing and debugging. Setting this enables APC for the CLI version of PHP. Under normal circumstances, it is not ideal to create, populate and destroy the APC cache on every CLI request, but for various test scenarios it is useful to be able to enable APC for the CLI version of PHP easily.

Maybe APC will store the opcodes in memory, but as the PHP executable dies at the end of the script, that memory will be lost : it will not persist between executions of the script.

So opcode-cache in APC is useless in CLI mode : it will not optimize anything, as PHP will still have to re-compile the source to opcodes each time PHP's executable is launched.


Actually, APC doesn't "optimize" : the standard way of executing a PHP script is like this :

  • read the file, and compile it into opcodes
  • execute the opcodes

What APC does is store in opcodes in memory, so the execution of a PHP script becomes :

  • read the opcodes from memory (much faster than compiling the source-code)
  • execute the opcodes

But this means you must have some place in memory to store the opcodes. When running PHP as an Apache module, Apache is responsible for the persistence of that memory segment... When PHP is run from CLI, there is nothing to keep the memory segment there, so it is destroyed at the end of PHP's execution.
(I don't know how it works exactly, but it's something like that, at least in the principles, even if my words are not very "technical" ^^ )


Or, by "optimization" you mean something else than opcode cache, like the configuration directive apc.optimization ? If so, this one has been removed in APC 3.0.13

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