140 lines
4.4 KiB
Markdown
140 lines
4.4 KiB
Markdown
# Introduction
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Composer is a tool for dependency management in PHP. It allows you to declare
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the dependent libraries your project needs and it will install them in your
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project for you.
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## Dependency management
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Composer is not a package manager. Yes, it deals with "packages" or libraries, but
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it manages them on a per-project basis, installing them in a directory (e.g. `vendor`)
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inside your project. By default it will never install anything globally. Thus,
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it is a dependency manager.
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This idea is not new and Composer is strongly inspired by node's [npm](http://npmjs.org/)
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and ruby's [bundler](http://gembundler.com/). But there has not been such a tool
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for PHP.
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The problem that Composer solves is this:
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a) You have a project that depends on a number of libraries.
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b) Some of those libraries depend on other libraries .
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c) You declare the things you depend on
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d) Composer finds out which versions of which packages need to be installed, and
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installs them (meaning it downloads them into your project).
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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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{
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"require": {
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"monolog/monolog": "1.2.*"
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}
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}
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We are simply stating that our project requires some `monolog/monolog` package,
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any version beginning with `1.2`.
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## Installation - *nix
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### Downloading the Composer Executable
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#### Locally
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To actually get Composer, we need to do two things. The first one is installing
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Composer (again, this means downloading it into your project):
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$ curl -s https://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 file is the Composer binary. It is a PHAR (PHP
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archive), which is an archive format for PHP which can be run on the command
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line, amongst other things.
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You can install Composer to a specific directory by using the `--install-dir`
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option and providing a target directory (it can be an absolute or relative path):
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$ curl -s https://getcomposer.org/installer | php -- --install-dir=bin
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#### Globally
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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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You can run these commands to easily access `composer` from anywhere on your system:
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$ curl -s https://getcomposer.org/installer | php
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$ sudo mv composer.phar /usr/local/bin/composer
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Then, just run `composer` in order to run Composer instead of `php composer.phar`.
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## Installation - Windows
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### Using the Installer
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This is the easiest way to get Composer set up on your machine.
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Download and run [Composer-Setup.exe](https://getcomposer.org/Composer-Setup.exe),
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it will install the latest Composer version and set up your PATH so that you can
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just call `composer` from any directory in your command line.
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### Manual Installation
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Change to a directory on your `PATH` and run the install snippet to download
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composer.phar:
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C:\Users\username>cd C:\bin
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C:\bin>php -r "eval('?>'.file_get_contents('https://getcomposer.org/installer'));"
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Create a new `.bat` file alongside composer:
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C:\bin>notepad composer.bat
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Paste the following in, it simply proxies all arguments to composer:
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@ECHO OFF
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SET composerScript=composer.phar
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php "%~dp0%composerScript%" %*
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Save the file. Close your current terminal. Test usage with a new terminal:
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C:\Users\username>composer -V
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Composer version 27d8904
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C:\Users\username>
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## Using Composer
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Next, run the `install` command to resolve and download dependencies:
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$ php composer.phar install
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If you did a global install and do not have the phar in that directory
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run this instead:
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$ composer install
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This will download monolog into the `vendor/monolog/monolog` directory.
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## Autoloading
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Besides downloading the library, Composer also prepares an autoload file that's
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capable of autoloading all of the classes in any of the libraries that it
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downloads. To use it, just add the following line to your code's bootstrap
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process:
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require 'vendor/autoload.php';
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Woh! Now start using monolog! To keep learning more about Composer, keep
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reading the "Basic Usage" chapter.
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[Basic Usage](01-basic-usage.md) →
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