Question

This question is about the PHP parsing engine.

When I include a file multiple times in a single runtime, does PHP tokenize it every time or does it keep a cache and just run the compiled code on subsequent inclusions?

EDIT: More details: I am not using an external caching mechanism and I am dealing with the same file being included multiple times during the same request.

EDIT 2: The file I’m trying to include contains procedural code. I want it to be executed every time I include() it, I am just curious if PHP internally keeps track of the tokenized version of the file for speed reasons.

Answer 1

By default the file is parsed every time it is (really) included, even within the same php instance.
But there are opcode caches like e.g. apc

<?php
$i = 'include_test.php';

file_put_contents($i, '<?php $x = 1;');
include $i;
echo $x, ' ';

file_put_contents($i, '<?php $x = 2;');
include $i;
echo $x, ' '

1 2

(ok, weak proof. PHP could check whether the file’s mtime has changed. And that what apc does, I think. But without a cache PHP really doesn’t)