The command "composer install" is used in PHP projects to install all the required dependencies defined in the composer.lock file.
Composer is a dependency management tool for PHP that allows developers to declare the libraries their project depends on and manages the installation/update of those libraries.
When you run "composer install" in your project directory, Composer scans the composer.json file, which lists all the dependencies required for the project. It then resolves the dependencies and installs the necessary packages from the Packagist repository (or any other repositories specified in composer.json).
Composer also creates a composer.lock file, which records the exact versions of the dependencies that were installed. The composer.lock file is used to ensure the same versions are used in future installations, providing consistency across different environments.
Running "composer install" also triggers the autoloader generation process, which generates the necessary class autoloading files to make it easy for your project to load the libraries.
In summary, the "composer install" command installs all the necessary dependencies and their specific versions, as defined in composer.json, for your PHP project.