Composer: Speeding up class autoloading

The Use Case

Those of you using Composer have probably tried speeding up the PHP autoloading mechanism using the option:

--optimize-autoloader (-o): Convert PSR-0 autoloading to classmap to get a faster autoloader. This is recommended especially for production, but can take a bit of time to run so it is currently not done by default.

The Goal

While it can certainly make your autoloading faster it can be further optimized if you are using PSR-0-like autoloading mechanism and have quite a lot of classes.

The Problem

The problem with the classmap strategy and the nature of PHP is that there is no (easy) way to have a persistent variable across requests containing the classmap. Even if you are using APC, a PHP file returning a big array will always take some CPU cycles and memory because the array still needs to be recreated from the cached opcodes. This can even take a big portion of your request's response time when you have hundreds or thousands of classes like it is the case with eZ Publish 5 being based on Symfony, where about 2 600 classes are involved.

The Solution

I came across a quite simple solution that can surely be automatized from inside Composer itself.

Given that most dependencies of eZ Publish 5 are using the PSR-0 standard, I created a vendor/PSR-0 directory containing symbolic links to all relevant elements in such a way that there is a direct match between a namespaced class and the file system from a unique root directory:

$ tree vendor/PSR-0/
vendor/PSR-0/
├── Assetic -> ../kriswallsmith/assetic/src/Assetic/
├── eZ -> ../ezsystems/ezpublish/eZ/
├── EzSystems -> ../../src/EzSystems/
├── Monolog -> ../monolog/monolog/src/Monolog/
├── Psr -> ../psr/log/Psr
├── Sensio -> ../sensio/generator-bundle/Sensio/
├── Symfony
│   ├── Bridge -> ../../symfony/symfony/src/Symfony/Bridge/
│   ├── Bundle
│   │   ├── AsseticBundle -> ../../../symfony/assetic-bundle/Symfony/Bundle/AsseticBundle/
│   │   ├── FrameworkBundle -> ../../../symfony/symfony/src/Symfony/Bundle/FrameworkBundle/
│   │   ├── MonologBundle -> ../../../symfony/monolog-bundle/Symfony/Bundle/MonologBundle/
│   │   ├── SecurityBundle -> ../../../symfony/symfony/src/Symfony/Bundle/SecurityBundle/
│   │   ├── SwiftmailerBundle -> ../../../symfony/swiftmailer-bundle/Symfony/Bundle/SwiftmailerBundle/
│   │   ├── TwigBundle -> ../../../symfony/symfony/src/Symfony/Bundle/TwigBundle/
│   │   └── WebProfilerBundle -> ../../../symfony/symfony/src/Symfony/Bundle/WebProfilerBundle/
│   ├── Cmf -> ../../../vendor/symfony-cmf/routing/Symfony/Cmf/
│   └── Component -> ../../symfony/symfony/src/Symfony/Component/
└── Twig -> ../twig/twig/lib/Twig/

Once this has been setup, instead of using the usual Composer's autoload.php file, a custom autoloader is created for loading classes directly from that tree:

spl_autoload_register(
    function ( $className )
    {
        if (
            strpos( $className, "Symfony\\" ) === 0 ||
            strpos( $className, "Sensio\\" ) === 0 ||
            strpos( $className, "eZ\\" ) === 0 ||
            strpos( $className, "EzSystems\\" ) === 0 ||
            strpos( $className, "Monolog\\" ) === 0 ||
            strpos( $className, "Psr\\" ) === 0 ||
            strpos( $className, "Twig_" ) === 0 ||
            strpos( $className, "Assetic\\" ) === 0
        )
        {
            if (
                file_exists(
                    $path = __DIR__ . "/../vendor/PSR-0/" . str_replace( array( "_", "\\" ), "/", $className ) . ".php"
                )
            )
            {
                require $path;
            }
        }
        else
        {
            return;
        }
    },
    true
);

Conclusion

Once I did that change on a typical eZ Publish site configured with ezdemo package, my laptop was able to serve 227 reqs/second instead of the initial 176 reqs/second that is a 29% boost.

Action point

Composer team: any chance to be able to generate this automagically? :-)