66 lines
2.0 KiB
Markdown
66 lines
2.0 KiB
Markdown
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# Introduction
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Composer is a tool for dependency management in PHP. It allows you to declare
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the dependencies of your project and will install these dependencies for you.
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## Dependency management
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One important distinction to make is that composer is not a package manager. It
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deals with packages, but it manages them on a per-project basis. By default it
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will never install anything globally. Thus, it is a dependency manager.
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This idea is not new by any means. Composer is strongly inspired by
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node's [npm](http://npmjs.org/) and ruby's [bundler](http://gembundler.com/).
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But there has not been such a tool for PHP so far.
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The problem that composer solves is the following. You have a project that
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depends on a number of libraries. Some of libraries have dependencies of their
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own. You declare the things you depend on. Composer will then go ahead and
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find out which versions of which packages need to be installed, and install
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them.
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## Declaring dependencies
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Let's say you are creating a project, and you need a library that does logging.
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You decide to use [monolog](https://github.com/Seldaek/monolog). In order to
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add it to your project, all you need to do is create a `composer.json` file
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which describes the project's dependencies.
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```json
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{
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"require": {
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"monolog/monolog": "1.0.2"
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}
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}
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```
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We are simply stating that our project requires the `monolog/monolog` package,
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version `1.0.2`.
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## Installation
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To actually get it, we need to do two things. The first one is installing
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composer:
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$ curl -s http://getcomposer.org/installer | php
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This will just check a few PHP settings and then download `composer.phar` to
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your working directory. This is the composer binary.
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After that we run the command for installing all dependencies:
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$ php composer.phar install
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This will download monolog and dump it into `vendor/monolog/monolog`.
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## Autoloading
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After this you can just add the following line to your bootstrap code to get
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autoloading:
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```php
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require 'vendor/.composer/autoload.php';
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```
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That's all it takes to have a basic setup.
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