Open Source Software for PHP
ZPanel
ZPanel is a free web hosting control panel for macOS, Linux and Windows-based servers. With ZPanel it's easy to manage your server for web hosting related tasks such as setting up server environments, managing DNS reccords and configuring SMTP. The software is written in PHP and released as open source software under the GNU General Public License 3.0.
Laravel
Laravel is an extremely popular, free and open source web application framework with expressive, elegant syntax. The framework is written in PHP and provides a developer experience that rival most web application frameworks on the market today. The structure and built-in features of Laravel allows developers to build web applications faster. Instead of setting up tooling and configuring settings, developers can focus on the important task at hand, making their ideas into reality.
Guzzle
PHP HTTP client that makes it easy to send HTTP requests and trivial to integrate with web services
Zend Framework
Zend Framework is a web application framework written in PHP that has an open architecture based on middleware or MVC which follows PHP-FIG standards. The framework is designed to follow the best security practices and stores passwords using bcrypt and encrypts data with AES-256. Zend Framework consists of multiple PHP packages that are designed to run separately or work interchangeably together. With Zend Framework you can develop web applications and services using PHP 5.6+, while writing 100% object-oriented code, broad spectrum of PHP specific features.
FuelPHP
FuelPHP is a MVC (Model-View-Controller) framework that was designed from the ground up to build scalable web applications written in PHP. Out-of-the-box, FuelPHP supports HVMC as a part of its arcitecture. The Hierarchical-Model-View-Controller (HMVC) pattern is a direct extension to the MVC pattern that manages to solve many of the scalability issues when building applications. HMVC is a collection of traditional MVC triads operating as one application. Each triad is completely independent and can execute without the presence of any other. All requests made to triads must use the controller interface, never loading models or libraries outside of their own domain. FuelPHP is released as a free and open source framework under the MIT License and can be used for commercial and personal projects alike.
Magento
Magento is a free and open-source self-hosted e-commerce platform written in PHP. The software is released under the Open Software License v3.0 and has been openly developed since March 31, 2008. Today Magento powers over 200,000 online shops globally and has grown into one of the most mature and trusted open source e-commerce platform. With Magento businesses can manage their online retail business with sophisticated tools that has been tried and tested.
OpenCart
OpenCart is a free and open source e-commerce and shopping cart system written in PHP. With OpenCart merchants can create their own online store at a minimal cost, simply get a web host and start installing the software. The OpenCart software includes all the necessary features to run a online stores and connects to over 20+ payment gateways and 8 shipping methods.
osCommerce
osCommerce is an open-source shopping cart system that you can use to create online store. It is one of the oldest and most comprehensive open-source shopping cart on the market today. The software is written in PHP and is self-hosted, allowing you to have complete access to, and total control of your online store and data. osCommerce is a 20+ years old, community-driven project and includes over 9,000 add-ons that can be used to customize and add further functionality to your online store.
bbPress
bbPress is forum software from the creators of WordPress. With bbPress you can quickly setup a forum for asyncronous discussion and subscriptions for your WordPress-powered site.
Drupal Commerce
Drupal Commerce is a free and open-source eCommerce module for Drupal. With Drupal Commerce, people can start selling products from their Drupal-powered websites by simply installing and configuring the module. Drupal Commerce provides extra extensions that can be used to further improve and extend on the features of the module.