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Symfony is fast, right out of the box. Of course, if you really need speed, there are many ways that you can make Symfony even faster. In this chapter, you'll explore some of the ways to make your Symfony application even faster.
The first thing that you should do to improve your performance is to use a "byte code cache". These caches store the compiled PHP files to avoid having to recompile them for every request.
Using a byte code cache really has no downside, and Symfony has been architected to perform really well in this type of environment.
Most byte code caches monitor the source files for changes. This ensures that if the source of a file changes, the byte code is recompiled automatically. This is really convenient, but it adds overhead.
For this reason, some byte code caches offer an option to disable these checks.
For example, to disable these checks in APC, simply add
apc.stat=0 to your
When disabling these checks, it will be up to the server administrators to ensure that the cache is cleared whenever any source files change. Otherwise, the updates you've made in the application won't be seen.
For the same reasons, the byte code cache must also be cleared when deploying
the application (for example by calling
apc_clear_cache() PHP function when
using APC and
opcache_reset() when using OPcache).
In PHP, the CLI and the web processes don't share the same OPcache. This
means that you cannot clear the web server OPcache by executing some command
in your terminal. You either need to restart the web server or call the
opcache_reset() functions via the web server
(i.e. by having these in a script that you execute over the web).
By default, PHP's OPcache saves up to 2,000 files in the byte code cache. This number is too low for the typical Symfony application, so you should set a higher limit with the opcache.max_accelerated_files configuration option:
; php.ini opcache.max_accelerated_files = 20000
PHP uses an internal cache to store the result of mapping file paths to their real and absolute file system paths. This increases the performance for applications like Symfony that open many PHP files, especially on Windows systems.
By default PHP sets a
16K which is too low for
Symfony. Consider updating this value at least to
4096K. In addition, cached
paths are only stored for
120 seconds by default. Consider updating this
value too using the
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; php.ini realpath_cache_size=4096K realpath_cache_ttl=600
By default, the Symfony Standard Edition uses Composer's autoloader in the autoload.php file. This autoloader is easy to use, as it will automatically find any new classes that you've placed in the registered directories.
Unfortunately, this comes at a cost, as the loader iterates over all configured
namespaces to find a particular file, making
file_exists() calls until it
finally finds the file it's looking for.
The simplest solution is to tell Composer to build an optimized "class map",
which is a big array of the locations of all the classes and it's stored
The class map can be generated from the command line, and might become part of your deploy process:
$ composer dump-autoload --optimize --no-dev --classmap-authoritative
- Dumps every PSR-0 and PSR-4 compatible class used in your application.
- Excludes the classes that are only needed in the development environment (e.g. tests).
- Prevents Composer from scanning the file system for classes that are not found in the class map.
Another solution is to cache the location of each class after it's located the first time. Symfony comes with a class - ApcClassLoader - that does exactly this. To use it, just adapt your front controller file. If you're using the Standard Distribution, make the following changes:
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// 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); // ...
For more details, see Cache a Class Loader.
When using the APC autoloader, if you add new classes, they will be found automatically and everything will work the same as before (i.e. no reason to "clear" the cache). However, if you change the location of a particular namespace or prefix, you'll need to flush your APC cache. Otherwise, the autoloader will still be looking at the old location for all classes inside that namespace.
To ensure optimal flexibility and code reuse, Symfony applications leverage a variety of classes and 3rd party components. But loading all of these classes from separate files on each request can result in some overhead. To reduce this overhead, the Symfony Standard Edition provides a script to generate a so-called bootstrap file, consisting of multiple classes definitions in a single file. By including this file (which contains a copy of many of the core classes), Symfony no longer needs to include any of the source files containing those classes. This will reduce disc IO quite a bit.
If you're using the Symfony Standard Edition, then you're probably already
using the bootstrap file. To be sure, open your front controller (usually
app.php) and check to make sure that the following line exists:
Note that there are two disadvantages when using a bootstrap file:
- the file needs to be regenerated whenever any of the original sources change (i.e. when you update the Symfony source or vendor libraries);
- when debugging, one will need to place break points inside the bootstrap file.
If you're using the Symfony Standard Edition, the bootstrap file is automatically
rebuilt after updating the vendor libraries via the
composer install command.
Even when using a byte code cache, performance will improve when using a bootstrap
file since there will be fewer files to monitor for changes. Of course if this
feature is disabled in the byte code cache (e.g.
apc.stat=0 in APC), there
is no longer a reason to use a bootstrap file.