To start using *Composer* in your project, all you need is a *composer*.json file. This file describes the dependencies of your project and may contain other ...[See more](https://getcomposer.org/doc/01-basic-usage.md#:~:text=To%20start%20using%20Composer%20in,contain%20other%20metadata%20as%20well.)
[Composer basics](https://www.google.com/search?q=Composer+basics&oq=composer+basics&gs_lcrp=EgZjaHJvbWUyCggAEEUYFhgeGDkyBwgBEAAYgAQyCAgCEAAYFhgeMggIAxAAGBYYHjIICAQQABgWGB4yCAgFEAAYFhgeMgoIBhAAGAoYFhgeMggIBxAAGBYYHjIICAgQABgWGB4yCAgJEAAYFhge0gEIMTkyN2owajeoAgCwAgA&sourceid=chrome&ie=UTF-8&mstk=AUtExfDNRmLbpRL42uA4wmKxDpK5P0obg_UF98bUXq-y5SBOgs1lXg8WwHYgcAgDe2ixABk0ja_bOoBxDSQorJbf1TMgSWuSVYUPRngAu-cqTKA1UtkEz2YNYKd77PesbFAdiw0yK-hT6APc5gOl4lcAYhAHZmyQS_QBbU1MnMMto322xhqdNXdNj5J2VicI6GO0wST-h6qIBoRhZC_qhO3IWvxR-FCWFV09glgteGcXduC7kwJ8Ws5KIUokhHM-uNLkiadRjlkoHKmLUzIoy5c93Xhc&csui=3&ved=2ahUKEwjpvsDj7rSRAxXRzqACHeEfPAEQgK4QegQIARAD) revolve around it being a **dependency manager for PHP**, letting you declare libraries your project needs in a `composer.json` file, and then automatically installing, updating, and autoloading them via simple command-line tools like `composer install` and `composer require`, saving immense time by managing third-party code (like Guzzle, PHPUnit) so you don't have to manually find and manage them. It works per-project, creating a `vendor` directory and an `autoload.php` file for seamless class loading, similar to npm for JavaScript or Bundler for Ruby.
This video provides a beginner-friendly introduction to Composer:
1. **Dependency Declaration**: Define your project's external libraries (packages) in `composer.json` (e.g., `ramsey/uuid` for UUIDs, `guzzlehttp/guzzle` for HTTP requests).
2. **Installation**: Run `composer install` in your project's root directory to download and install declared dependencies into the `vendor` folder, respecting versions in `composer.lock` if it exists, or creating it if not.
3. **Adding New Packages**: Use `composer require vendor/package-name` to add a new library, which updates `composer.json`, `composer.lock`, and installs the package.
4. **[Autoloading](https://www.google.com/search?q=Autoloading&oq=composer+basics&gs_lcrp=EgZjaHJvbWUyCggAEEUYFhgeGDkyBwgBEAAYgAQyCAgCEAAYFhgeMggIAxAAGBYYHjIICAQQABgWGB4yCAgFEAAYFhgeMgoIBhAAGAoYFhgeMggIBxAAGBYYHjIICAgQABgWGB4yCAgJEAAYFhge0gEIMTkyN2owajeoAgCwAgA&sourceid=chrome&ie=UTF-8&mstk=AUtExfDNRmLbpRL42uA4wmKxDpK5P0obg_UF98bUXq-y5SBOgs1lXg8WwHYgcAgDe2ixABk0ja_bOoBxDSQorJbf1TMgSWuSVYUPRngAu-cqTKA1UtkEz2YNYKd77PesbFAdiw0yK-hT6APc5gOl4lcAYhAHZmyQS_QBbU1MnMMto322xhqdNXdNj5J2VicI6GO0wST-h6qIBoRhZC_qhO3IWvxR-FCWFV09glgteGcXduC7kwJ8Ws5KIUokhHM-uNLkiadRjlkoHKmLUzIoy5c93Xhc&csui=3&ved=2ahUKEwjpvsDj7rSRAxXRzqACHeEfPAEQgK4QegQIBBAE)**: Include `require 'vendor/autoload.php';` at the top of your main PHP file to automatically load classes from installed packages, eliminating manual `require` statements.
5. **Updating/Managing**: Use `composer update` to find newer versions of packages, and `composer update vendor/package` to update specific ones.
You can watch this video to see how to use Composer to install packages:
- `composer.json`: Your project's manifest, listing dependencies and versions.
- `composer.lock`: Locks exact package versions to ensure consistent installations across environments.
- `vendor/`: Directory where Composer installs all downloaded packages and the autoloader.
This video explains the initial setup and use of Composer:
- `composer install`: Installs dependencies from `composer.json` / `composer.lock`.
- `composer require vendor/package`: Adds and installs a new package.
- `composer update`: Updates packages to newer compatible versions.
- `composer dump-autoload`: Regenerates the autoloader.
# How to switch in different composer version in ubuntu
To switch between different Composer versions on Ubuntu, particularly between major versions like Composer 1 and Composer 2, you can use the `self-update` command with specific flags.
**Switching between Composer 1 and Composer 2:
**
To switch to Composer 1.
```
composer self-update --1
```
To switch to Composer 2.
```
composer self-update --2
```
Other useful `self-update` commands:
- **To update to the latest stable version (usually Composer 2):**
```
composer self-update
```
- **To revert to the previous Composer version:**
```
composer self-update --rollback
```
- **To preview a new Composer version before updating:**
```
composer self-update --preview
```
Important Notes:
- If you encounter permission errors when running `composer self-update`, you might need to run it with `sudo`, like `sudo composer self-update --2`. However, be cautious when using `sudo` with Composer, as it can sometimes lead to permission issues in your user's home directory.
- Ensure your PHP environment is compatible with the Composer version you are switching to. Different Composer versions might have different PHP version requirements.
- After switching versions, you can verify the current Composer version by running: