How to Create a Composer Package in PHP: Step-by-Step Guide

To create a Composer package in PHP, start by creating a composer.json file with your package details and dependencies. Then write your PHP code inside a proper namespace and directory structure, and finally publish your package to Packagist or use it locally via Composer.

Syntax

The composer.json file defines your package metadata and dependencies. Key parts include:

• name: Your package name in vendor/package format.
• description: A short description of your package.
• autoload: Defines how your PHP classes are loaded, usually with PSR-4 standard.
• require: Lists other packages your package depends on.

json

{
  "name": "vendor/package",
  "description": "A short description of your package",
  "type": "library",
  "autoload": {
    "psr-4": {
      "Vendor\\Package\\": "src/"
    }
  },
  "require": {}
}

Example

This example shows a simple PHP package with a class and the composer.json file. It demonstrates how to set up autoloading and use the package.

json+php

{
  "name": "example/hello-world",
  "description": "A simple hello world package",
  "type": "library",
  "autoload": {
    "psr-4": {
      "Example\\HelloWorld\\": "src/"
    }
  },
  "require": {}
}

// File: src/Greet.php
<?php
namespace Example\HelloWorld;

class Greet {
    public function sayHello(): string {
        return "Hello, Composer Package!";
    }
}

// Usage example (in another project):
// require 'vendor/autoload.php';
// $greet = new \Example\HelloWorld\Greet();
// echo $greet->sayHello();

Output

Hello, Composer Package!

Common Pitfalls

Common mistakes when creating a Composer package include:

• Incorrect autoload paths causing classes not to load.
• Missing or wrong namespace declarations in PHP files.
• Not committing composer.json or composer.lock files to version control.
• Forgetting to register the package on Packagist for public use.

Always test autoloading locally with composer dump-autoload and composer install.

php

<?php
// Wrong namespace example
namespace WrongNamespace;

class Greet {}

// Correct namespace example
namespace Example\HelloWorld;

class Greet {}

Quick Reference

Steps to create and publish a Composer package:

1. Create composer.json with metadata and autoload info.
2. Write your PHP classes inside the directory matching your namespace.
3. Test autoloading locally with Composer commands.
4. Push your code to a public Git repository (e.g., GitHub).
5. Submit your package to Packagist for public availability.

Key Takeaways

Create a valid composer.json with correct name, description, and autoload settings.

Use PSR-4 namespaces matching your directory structure for autoloading.

Test your package locally with composer install and dump-autoload before publishing.

Publish your package on Packagist to make it available to others.

Avoid common mistakes like wrong namespaces or missing files in version control.