165 lines
6.1 KiB
Markdown
165 lines
6.1 KiB
Markdown
# Basic usage
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## Installation
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To install composer, simply run this command on the command line:
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$ curl -s http://getcomposer.org/installer | php
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This will perform some checks on your environment to make sure you can
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actually run it.
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This will download `composer.phar` and place it in your working directory.
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`composer.phar` is the composer binary. It is a PHAR (PHP archive), which
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is an archive format for PHP which can be run on the command line, amongst
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other things.
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You can place this file anywhere you wish. If you put it in your `PATH`,
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you can access it globally. On unixy systems you can even make it
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executable and invoke it without `php`.
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To check if composer is working, just run the PHAR through `php`:
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$ php composer.phar
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This should give you a list of available commands.
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**Note:** You can also perform the checks only without downloading composer
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by using the `--check` option. For more information, just use `--help`.
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$ curl -s http://getcomposer.org/installer | php -- --help
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## Project setup
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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
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other metadata as well.
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The [JSON format](http://json.org/) is quite easy to write. It allows you to
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define nested structures.
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The first (and often only) thing you specify in `composer.json` is the
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`require` key. You're simply telling composer which packages your project
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depends on.
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```json
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{
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"require": {
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"monolog/monolog": "1.0.*"
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}
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}
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```
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As you can see, `require` takes an object that maps package names to versions.
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## Package names
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The package name consists of a vendor name and the project's name. Often these
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will be identical. The vendor name exists to prevent naming clashes. It allows
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two different people to create a library named `json`, which would then just be
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named `igorw/json` and `seldaek/json`.
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Here we are requiring `monolog/monolog`, so the vendor name is the same as the
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project's name. For projects with a unique name this is recommended. It also
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allows adding more related projects under the same namespace later on. If you
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are maintaining a library, this would make it really easy to split it up into
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smaller decoupled parts.
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If you don't know what to use as a vendor name, your GitHub username is usually
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a good bet.
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## Package versions
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We are also requiring the version `1.0.*` of monolog. This means any version
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in the `1.0` development branch. It would match `1.0.0`, `1.0.2` and `1.0.20`.
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Version constraints can be specified in a few different ways.
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* **Exact version:** You can specify the exact version of a package, for
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example `1.0.2`. This is not used very often, but can be useful.
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* **Range:** By using comparison operators you can specify ranges of valid
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versions. Valid operators are `>`, `>=`, `<`, `<=`. An example range would be `>=1.0`. Youcan define multiple of these, separated by comma:
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`>=1.0,<2.0`.
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* **Wildcard:** You can specify a pattern with a `*` wildcard. The previous
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`>=1.0,<2.0` example could also be written as `1.0.*`.
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## Installing dependencies
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To fetch the defined dependencies into the local project, you simply run the
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`install` command of `composer.phar`.
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$ php composer.phar install
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This will find the latest version of `monolog/monolog` that matches the
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supplied version constraint and download it into the the `vendor` directory.
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It's a convention to put third party code into a directory named `vendor`.
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In case of monolog it will put it into `vendor/monolog/monolog`.
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**Tip:** If you are using git for your project, you probably want to add
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`vendor` into your `.gitignore`. You really don't want to add all of that
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code to your repository.
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Another thing that the `install` command does is it adds a `composer.lock` file
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into your project root.
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## Lock file
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After installing the dependencies, composer writes the list of the exact
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versions it installed into a `composer.lock` file. This locks the project
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to those specific versions.
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**Commit your project's `composer.lock` into version control.**
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The reason is that anyone who sets up the project should get the same version.
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The `install` command will check if a lock file is present. If it is, it will
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use the versions specified there. If not, it will resolve the dependencies and
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create a lock file.
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If any of the dependencies gets a new version, you can update to that version
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by using the `update` command. This will fetch the latest matching versions and
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also update the lock file.
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$ php composer.phar update
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## Autoloading
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For libraries that follow the [PSR-0](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md) naming standard, composer generates
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a `vendor/.composer/autoload.php` file for autoloading. You can simply include this file and you will get autoloading for free.
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```php
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require 'vendor/.composer/autoload.php';
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```
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This makes it really easy to use third party code, because you really just have to add one line to `composer.json` and run `install`. For monolog, it means that we can just start using classes from it, and they will be autoloaded.
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```php
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$log = new Monolog\Logger('name');
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$log->pushHandler(new Monolog\Handler\StreamHandler('app.log', Logger::WARNING));
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$log->addWarning('Foo');
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```
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You can even add your own code to the autoloader by adding an `autoload` key to `composer.json`.
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```json
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{
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"autoload": {
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"psr-0": {"Acme": "src/"}
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}
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}
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```
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This is a mapping from namespaces to directories. The `src` directory would be in your project root. An example filename would be `src/Acme/Foo.php` containing a `Acme\Foo` class.
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After adding the `autoload` key, you have to re-run `install` to re-generate the `vendor/.composer/autoload.php` file.
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Including that file will also return the autoloader instance, so you can add retrieve it and add more namespaces. This can be useful for autoloading classes in a test suite, for example.
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```php
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$loader = require 'vendor/.composer/autoload.php';
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$loader->add('Acme\Test', __DIR__);
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```
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**Note:** Composer provides its own autoloader. If you don't want to use that one, you can just include `vendor/.composer/autoload_namespaces.php`, which returns an associative array mapping namespaces to directories.
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