# Runtime Composer utilities While Composer is mostly used around your project to install its dependencies, there are a few things which are made available to you at runtime. If you need to rely on some of these in a specific version, you can require the `composer-runtime-api` package. ## Autoload The autoloader is the most used one, and is already covered in our [basic usage guide](01-basic-usage.md#autoloading). It is available in all Composer versions. ## Installed versions composer-runtime-api 2.0 introduced a new `Composer\InstalledVersions` class which offers a few static methods to inspect which versions are currently installed. This is automatically available to your code as long as you include the Composer autoloader. The main use cases for this class are the following: ### Knowing whether package X (or virtual package) is present ```php \Composer\InstalledVersions::isInstalled('vendor/package'); // returns bool \Composer\InstalledVersions::isInstalled('psr/log-implementation'); // returns bool ``` Note that this can not be used to check whether platform packages are installed. ### Knowing whether package X is installed in version Y > **Note:** To use this, your package must require `"composer/semver": "^2.0"`. ```php use Composer\Semver\VersionParser; \Composer\InstalledVersions::satisfies(new VersionParser, 'vendor/package', '2.0.*'); \Composer\InstalledVersions::satisfies(new VersionParser, 'psr/log-implementation', '^1.0'); ``` This will return true if e.g. vendor/package is installed in a version matching `2.0.*`, but also if the given package name is replaced or provided by some other package. ### Knowing the version of package X > **Note:** This will return `null` if the package name you ask for is not itself installed > but merely provided or replaced by another package. We therefore recommend using satisfies() > in library code at least. In application code you have a bit more control and it is less > important. ```php // returns a normalized version (e.g. 1.2.3.0) if vendor/package is installed, // or null if it is provided/replaced, // or throws OutOfBoundsException if the package is not installed at all \Composer\InstalledVersions::getVersion('vendor/package'); ``` ```php // returns the original version (e.g. v1.2.3) if vendor/package is installed, // or null if it is provided/replaced, // or throws OutOfBoundsException if the package is not installed at all \Composer\InstalledVersions::getPrettyVersion('vendor/package'); ``` ```php // returns the package dist or source reference (e.g. a git commit hash) if vendor/package is installed, // or null if it is provided/replaced, // or throws OutOfBoundsException if the package is not installed at all \Composer\InstalledVersions::getReference('vendor/package'); ``` ### Knowing a package's own installed version If you are only interested in getting a package's own version, e.g. in the source of acme/foo you want to know which version acme/foo is currently running to display that to the user, then it is acceptable to use getVersion/getPrettyVersion/getReference. The warning in the section above does not apply in this case as you are sure the package is present and not being replaced if your code is running. It is nonetheless a good idea to make sure you handle the `null` return value as gracefully as possible for safety. ---- A few other methods are available for more complex usages, please refer to the source/docblocks of the class itself. ## Platform check composer-runtime-api 2.0 introduced a new `vendor/composer/platform_check.php` file, which is included automatically when you include the Composer autoloader. It verifies that platform requirements (i.e. php and php extensions) are fulfilled by the PHP process currently running. If the requirements are not met, the script prints a warning with the missing requirements and exits with code 104. To avoid an unexpected white page of death with some obscure PHP extension warning in production, you can run `composer check-platform-reqs --no-dev` as part of your deployment/build and if that returns a non-0 code you should abort. If you for some reason do not want to use this safety check, and would rather risk runtime errors when your code executes, you can disable this by setting the [`platform-check`](06-config.md#platform-check) config option to `false`. ← [Config](06-config.md) | [Community](08-community.md) →