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 article, you'll explore some of the ways to make your Symfony application even faster.

Use a Byte Code Cache (e.g. OPcache)

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.

There are a number of byte code caches available, some of which are open source. As of PHP 5.5, PHP comes with OPcache built-in. For older versions, the most widely used byte code cache is APC.


If your server still uses the legacy APC PHP extension, install the APCu Polyfill component in your application to enable compatibility with APCu PHP functions and unlock support for advanced Symfony features, such as the APCu Cache adapter.

Using a byte code cache really has no downside, and Symfony has been designed to perform really well in this type of environment.

Monitoring Source File Changes

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 php.ini configuration.

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. These are some of the possible solutions:

  1. Restart the web server;
  2. Call the apc_clear_cache or opcache_reset functions via the web server (i.e. by having these in a script that you execute over the web);
  3. Use the cachetool utility to control APC and OPcache from the CLI.

Optimizing all the Files Used by Symfony

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

Configure the PHP realpath Cache

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.

Consider increasing the realpath_cache_size and realpath_cache_ttl:

; php.ini
; 4096k is the default value in PHP 7.2

Use Composer's Class Map Functionality

Symfony uses Composer's autoloader. 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 in vendor/composer/autoload_classmap.php.

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.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.