ApcClassLoad does not work as written

[michael-lavaveshkul]

http://symfony.com/doc/2.8/performance.html#caching-the-autoloader-with-apc

This page currently has its app.php example written like this:

// app.php
// ...

use Symfony\Component\ClassLoader\ApcClassLoader;

$loader = require __DIR__.'/../app/autoload.php';
include_once __DIR__.'/../app/bootstrap.php.cache';

// Use APC for autoloading to improve performance
// Change 'sf2' by the prefix you want in order
// to prevent key conflict with another application
$loader = new ApcClassLoader('sf2', $loader);
$loader->register(true);

// ...

The problem is bootstrap.php.cache also sets $loader with this line up near the top with something like this:

$loader = require_once __DIR__.'/./autoload.php';

Because autoload.php was already loaded once, this line from bootstrap.php.cache sets $loader to true. Later in web/app.php, calling new ApcClassLoader('sf2', $loader); throws the following error:

Fatal error: Uncaught exception 'InvalidArgumentException' with message 'The class finder must implement a "findFile" method.' in /var/www/my_project/app/bootstrap.php.cache:2869 Stack trace:
# 0 /var/www/my_project/web/app.php(18): Symfony\Component\ClassLoader\ApcClassLoader->__construct('my_project', true)
# 1 /var/www/my_project/web/index.php(17): include_once('/var/www/my_project...')
# 2 {main} thrown in /var/www/my_project/app/bootstrap.php.cache on line 2869

Because $loader is true and no longer an instance of ClassLoader.

I entered this as an issue without a pull request because I wasn't sure what the fix should be. Users could be told to comment out $loader = require __DIR__.'/../app/autoload.php'; from web/app.php in the documentation, but I'm not sure if there's a better way to handle it.

Steps to reproduce:

1. Make sure you have apc enabled
2. Download and configure Symfony 2.8 project
3. Change web/app.php to match the example code above.
4. Try to visit app.php in your browser.
5. This should trigger the error I pasted above.

I did not test with other versions of Symfony.

[xabbuh]

Thanks for reporting this @michael-lavaveshkul. I have checked the code and this is indeed an issue. See #8057 for my attempt to fix it.

[michael-lavaveshkul]

Thanks, @xabbuh! The proposed fix works for me.