Composer

A composer is a tool for dependency management in PHP.

Composer is an application-level package manager for the PHP programming language that provides a standard format for managing dependencies of PHP software and required libraries.

It was developed by Nils Adermann and Jordi Boggiano, who continue to manage the project.

Installation:

1. Download Windows installer Composer-Setup.exe from the link https://getcomposer.org/download/
2. Run the Composer-Setup.exe file
3. You must have PHP installed on your system as Composer requires PHP 5.3.2+ to run.
4. Set PHP path c:\xampp\php\php.exe while setup.
5. Finish
6. Check installed composer version using the command

C:\Users\username>composer — version
Composer version 1.8.4 2019–02–11 10:52:10

Usage:

To start using Composer in your project, all you need is a composer.json file.

• composer.json:
  This file describes the dependencies of your project and may contain other metadata as well.
• require key:
  The first thing you specify in composer.json is the require key. You are simply telling Composer which packages your project depends on.

{
"require": {
"monolog/monolog": "1.0.*"
}
}

As you can see, require takes an object that maps package names (e.g. monolog/monolog) to version constraints (e.g. 1.0.*).

• vendor directory:
  The vendor directory is the conventional location for all third-party code in a project.
  In our example from above, you would end up with the Monolog source files in vendor/monolog/monolog/. If Monolog listed any dependencies, those would also be in folders under vendor/.

Autoloading

For libraries that specify autoload information, Composer generates a vendor/autoload.php file. You can simply include this file and start using the classes that those libraries provide without any extra work:

require __DIR__ . '/vendor/autoload.php';

$log = new Monolog\Logger('name');
$log->pushHandler(new Monolog\Handler\StreamHandler('app.log', Monolog\Logger::WARNING));
$log->addWarning('Test');

You can even add your own code to the autoloader by adding an autoload field to composer.json.

{
"autoload": {
"psr-4": {"DemoPackage\\": "src/"}
}
}

Composer will register a PSR-4 autoloader for the DemoPackage namespace.

You define a mapping from namespaces to directories. The src directory would be in your project root, on the same level as vendor directory is. An example filename would be src/Test.php containing an DemoPackage\Test class.

After adding the autoload field, you have to re-run this command:

php composer.phar dump-autoload

This command will re-generate the vendor/autoload.php file.

Including that file will also return the autoloader instance, so you can store the return value of the include call in a variable and add more namespaces. This can be useful for autoloading classes in a test suite, for example.

$loader = require __DIR__ . '/vendor/autoload.php';
$loader->addPsr4('DemoPackage\\Test\\', __DIR__);

In addition to PSR-4 autoloading, Composer also supports PSR-0, classmap and files autoloading.

Deprecated — As of 2014–10–21 PSR-0 has been marked as deprecated. PSR-4 is now recommended as an alternative.