How to use PHP Composer for dependency management?
Jul 13, 2025 am 02:00 AMComposer solves many problems with PHP dependency management. 1. Install Composer: Windows users use graphical installer, Linux/macOS users download and move to the system path through commands; 2. Initialize the project: Run composer init to create composer.json file; 3. Add dependencies: manually edit the file or use the composer require command to install the package; 4. Automatic loading: Introduce vendor/autoload.php to automatically load the class library, and custom classes can be automatically loaded by configuring the autoload field; 5. Update and unload dependencies: Use composer update and composer remove commands respectively.
PHP's dependency management was once a troublesome thing, manually downloading, introducing class libraries, and processing automatically loading, which is inefficient and prone to errors. After Composer appeared, these problems were basically solved. It has become the de facto standard tool in PHP projects.

Install Composer
Composer itself is a command line tool, and the installation method varies slightly on different systems.
- Windows users : It is recommended to use the official graphical installer ( getcomposer.org ), which will automatically configure environment variables.
- Linux/macOS user : You can install it using the following command:
php -r "copy('http://m.miracleart.cn/link/521eae94653641ec7be496db736ce3f6installer', 'composer-setup.php');" php composer-setup.php php -r "unlink('composer-setup.php');" sudo mv composer.phar /usr/local/bin/composer
After the installation is completed, enter composer --version
to see if the version number is displayed and confirm whether the installation is successful.

Initialize the project and add dependencies
After entering your project directory, run:
composer init
This command will guide you to create a composer.json
file that records the meta information and dependencies of the project.

There are two ways to add dependencies:
- Manually edit the
composer.json
file and write the required package name and version; - Use the command to install the package directly:
composer requires vendor/package
For example:
composer requires monolog/monolog
After execution, Composer will automatically download the package and its dependencies to vendor/
directory, and generate the automatic loading file vendor/autoload.php
. You only need to introduce this file in your code to use these class libraries directly.
Automatic loading and optimization
Composer not only helps you manage dependencies, but also automatically generates automatic loading mechanisms for classes.
By default, all class libraries installed through Composer can be loaded correctly as long as you use require 'vendor/autoload.php';
If you write the class yourself, you can also modify composer.json
to automatically load:
"autoload": { "psr-4": { "MyApp\\": "src/" } }
The above means: all classes under the namespace MyApp\
are placed in src/
directory. After configuration, run:
composer dump-autoload
In this way, the classes you write can also be automatically loaded like third-party libraries.
In the production environment, you can also add a -o
parameter to optimize the loading speed:
composer dump-autoload -o
Update and uninstall dependencies
Update dependencies are simple, you can use:
composer update
This will upgrade all dependencies to the latest compatible version according to the version rules defined in composer.json
.
If you want to update only a certain package:
composer update vendor/package
It is also convenient to uninstall a dependency:
composer remove vendor/package
Composer will automatically clean up related files and configurations.
Basically that's it. Composer is not complicated to use, but many newbies tend to get stuck in installation or automatic loading issues at the beginning. As long as you pay attention to the correspondence between paths and namespaces, most problems can be solved.
The above is the detailed content of How to use PHP Composer for dependency management?. For more information, please follow other related articles on the PHP Chinese website!

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