167 lines
5.8 KiB
Markdown
167 lines
5.8 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 libraries your project depends on and it will manage (install/update) them
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for you.
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## Dependency management
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Composer is **not** a package manager in the same sense as Yum or Apt are. Yes,
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it deals with "packages" or libraries, but it manages them on a per-project
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basis, installing them in a directory (e.g. `vendor`) inside your project. By
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default, it does not install anything globally. Thus, it is a dependency
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manager. It does however support a "global" project for convenience via the
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[global](03-cli.md#global) command.
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This idea is not new and Composer is strongly inspired by node's
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[npm](https://www.npmjs.com/) and ruby's [bundler](https://bundler.io/).
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Suppose:
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1. You have a project that depends on a number of libraries.
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2. Some of those libraries depend on other libraries.
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Composer:
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1. Enables you to declare the libraries you depend on.
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2. Finds out which versions of which packages can and need to be installed, and
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installs them (meaning it downloads them into your project).
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3. You can update all your dependencies in one command.
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See the [Basic usage](01-basic-usage.md) chapter for more details on declaring
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dependencies.
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## System Requirements
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Composer requires PHP 5.3.2+ to run. A few sensitive php settings and compile
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flags are also required, but when using the installer you will be warned about
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any incompatibilities.
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To install packages from sources instead of simple zip archives, you will need
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git, svn, fossil or hg depending on how the package is version-controlled.
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Composer is multi-platform and we strive to make it run equally well on Windows,
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Linux and macOS.
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## Installation - Linux / Unix / macOS
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### Downloading the Composer Executable
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Composer offers a convenient installer that you can execute directly from the
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command line. Feel free to [download this file](https://getcomposer.org/installer)
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or review it on [GitHub](https://github.com/composer/getcomposer.org/blob/master/web/installer)
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if you wish to know more about the inner workings of the installer. The source
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is plain PHP.
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There are in short, two ways to install Composer. Locally as part of your
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project, or globally as a system wide executable.
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#### Locally
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To install Composer locally, run the installer in your project directory. See
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[the Download page](https://getcomposer.org/download/) for instructions.
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The installer will check a few PHP settings and then download `composer.phar`
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to your working directory. This file is the Composer binary. It is a PHAR
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(PHP archive), which is an archive format for PHP which can be run on
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the command line, amongst other things.
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Now run `php composer.phar` in order to run Composer.
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You can install Composer to a specific directory by using the `--install-dir`
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option and additionally (re)name it as well using the `--filename` option. When
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running the installer when following
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[the Download page instructions](https://getcomposer.org/download/) add the
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following parameters:
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```sh
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php composer-setup.php --install-dir=bin --filename=composer
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```
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Now run `php bin/composer` in order to run Composer.
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#### Globally
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You can place the Composer PHAR anywhere you wish. If you put it in a directory
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that is part of your `PATH`, you can access it globally. On Unix systems you
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can even make it executable and invoke it without directly using the `php`
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interpreter.
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After running the installer following [the Download page instructions](https://getcomposer.org/download/)
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you can run this to move composer.phar to a directory that is in your path:
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```sh
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mv composer.phar /usr/local/bin/composer
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```
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If you like to install it only for your user and avoid requiring root permissions,
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you can use `~/.local/bin` instead which is available by default on some
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Linux distributions.
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> **Note:** If the above fails due to permissions, you may need to run it again
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> with sudo.
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> **Note:** On some versions of macOS the `/usr` directory does not exist by
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> default. If you receive the error "/usr/local/bin/composer: No such file or
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> directory" then you must create the directory manually before proceeding:
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> `mkdir -p /usr/local/bin`.
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> **Note:** For information on changing your PATH, please read the
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> [Wikipedia article](https://en.wikipedia.org/wiki/PATH_(variable)) and/or use
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> your search engine of choice.
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Now 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
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[Composer-Setup.exe](https://getcomposer.org/Composer-Setup.exe). It will
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install the latest Composer version and set up your PATH so that you can
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call `composer` from any directory in your command line.
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> **Note:** Close your current terminal. Test usage with a new terminal: This is
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> important since the PATH only gets loaded when the terminal starts.
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### Manual Installation
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Change to a directory on your `PATH` and run the installer following
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[the Download page instructions](https://getcomposer.org/download/)
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to download `composer.phar`.
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Create a new `composer.bat` file alongside `composer.phar`:
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Using cmd.exe:
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```sh
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C:\bin> echo @php "%~dp0composer.phar" %*>composer.bat
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```
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Using PowerShell:
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```sh
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PS C:\bin> Set-Content composer.bat '@php "%~dp0composer.phar" %*'
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```
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Add the directory to your PATH environment variable if it isn't already.
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For information on changing your PATH variable, please see
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[this article](https://www.computerhope.com/issues/ch000549.htm) and/or
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use your search engine of choice.
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Close your current terminal. Test usage with a new terminal:
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```sh
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C:\Users\username>composer -V
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Composer version 1.0.0 2016-01-10 20:34:53
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```
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## Using Composer
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Now that you've installed Composer, you are ready to use it! Head on over to the
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next chapter for a short and simple demonstration.
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[Basic usage](01-basic-usage.md) →
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