How to Build and Publish Your Own Composer Package for PHP Projects

Composer is a PHP dependency manager that automates downloading, installing, and autoloading libraries defined in a project's composer.json.

How Composer Works

It consists of three parts: the CLI tool, a package repository, and the code repository.

CLI Commands

The composer command provides operations such as create-project, require, remove, and clear-cache.

Repositories

Packagist

: the default public repository (https://packagist.org) that stores package metadata. Repository: the code host, typically GitHub or Gitee.

Autoloading

Composer generates autoload files that follow PSR‑0 and PSR‑4 standards.

Step‑by‑Step Guide

Step 1 – Create a Git Repository

Create a public GitHub repository named hello and clone it locally.

git clone [email protected]:Tinywan/hello.git

Step 2 – Initialise composer.json

Run composer init and answer the prompts to generate a basic composer.json. Example output:

{
    "name": "tinywan/hello",
    "description": "How to build your own Composer package",
    "type": "library",
    "autoload": {
        "psr-4": {
            "Tinywan\\Hello\\": "src/"
        }
    },
    "authors": [
        {
            "name": "Tinywan",
            "email": "[email protected]"
        }
    ],
    "require": {}
}

Step 3 – Implement Package Functionality

Create a simple encryption class in src/Encryption.php that provides static encrypt and decrypt methods using OpenSSL.

<?php
declare(strict_types=1);

namespace tinywan\hello;

class Encryption
{
    public const AES_128_ECB = 'AES-128-ECB';

    public static function encrypt(string $data, string $key, string $algo = self::AES_128_ECB, string $iv = ''): string
    {
        $encryptedBytes = openssl_encrypt($data, $algo, $key, OPENSSL_RAW_DATA);
        return base64_encode($encryptedBytes);
    }

    public static function decrypt(string $data, string $key, string $algo = self::AES_128_ECB, string $iv = ''): string|false
    {
        return openssl_decrypt(base64_decode($data), $algo, $key, OPENSSL_RAW_DATA);
    }
}

Step 4 – Write PHPUnit Tests

Install PHPUnit as a dev dependency and create tests/EncryptionTest.php to verify encryption and decryption.

<?php
declare(strict_types=1);

class EncryptionTest extends \PHPUnit\Framework\TestCase
{
    public function test()
    {
        $data = 'OpenSourceStack';
        $key  = '53vYPpTJIR1aYFiFh0PppZzF';

        $encrypt = \tinywan\hello\Encryption::encrypt($data, $key);
        self::assertIsString($encrypt);

        $decrypt = \tinywan\hello\Encryption::decrypt($encrypt, $key);
        self::assertEquals($decrypt, $data);
    }
}

Run the test with:

$ vendor/phpunit/phpunit/phpunit tests/EncryptionTest.php

Step 5 – Commit and Tag

Add a .gitignore to exclude generated files and IDE directories, commit the code, and create a version tag.

build
vendor
.idea
.vscode
.phpunit*
composer.lock

$ git commit -m "init"
$ git tag v0.1
$ git push origin v0.1

Step 6 – Publish to Packagist

Register the package on packagist.org (or submit via the “Submit Package” page) so that Composer can retrieve its metadata.

Step 7 – Install the Package

Require the package in another project: composer require tinywan/hello dev-main For a stable release, use the tagged version (e.g., v0.1).

Conclusion

By following these steps you can create a reusable Composer library, test it with PHPUnit, publish it to Packagist, and consume it in any PHP project, avoiding duplicate code and leveraging the PHP ecosystem.