Tutorial :Is the same file tokenized every time I include it?


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.


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)


You should use a PHP bytecode cache such as APC. That will accomplish what you want, to re-use a compiled version of a PHP page on subsequent requests. Otherwise, PHP reads the file, tokenizes and compiles it on every request.


Look at include_once(). It will include it again.

Also if you are using objects. Look at __autoload()


I just wrote a basic test, much like VolkerK's. Here's what I tested:

<?php  file_put_contents('include.php','<?php echo $i . "<br />"; ?>');    for($i = 0; $i<10; $i++){      include('include.php');      if($i == 5){          file_put_contents('include.php','<?php echo $i+$i; echo "<br />"; ?>');      }  }    ?>  

This generated the following:

0  1  2  3  4  5  12  14  16  18  

So, unless it caches based on mtime of the file, it seems it parses every include. You would likely want to use include_once() instead of standard include(). Hope that helps!

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