Why PHP Should Switch to the MIT License: Benefits and Challenges

Background: Current PHP License Barriers

Since its inception, PHP core code has been released under PHP License 3.01 . This license imposes several constraints that hinder compatibility and commercial use:

Compatibility limits : Derivative works must retain the full original license and cannot use the “PHP” name for promotion, creating conflicts with licenses such as GPL.

Commercial concerns : Ambiguous terms around “derivative works” cause legal uncertainty for enterprises integrating PHP with proprietary code.

Ecosystem collaboration barriers : The restrictive clauses increase the risk of license conflicts when PHP is combined with projects that use permissive licenses, raising compliance costs.

Core Proposal: Migrate PHP to the MIT License

The proposal recommends re‑licensing the PHP core, the Zend Engine, the standard library, official extensions (e.g., PDO, MySQLi), and accompanying documentation under the MIT (3‑clause BSD) license. The MIT license permits unrestricted use, modification, distribution, and commercial exploitation, requiring only preservation of the original copyright notice.

Why Adopt the MIT License?

Improved ecosystem compatibility : MIT is compatible with virtually all major open‑source licenses (GPL, Apache, BSD, etc.), eliminating legal barriers for projects that wish to incorporate PHP code.

Lower adoption threshold : The simple terms reduce compliance effort for businesses and lower legal concerns for contributors.

Alignment with community practice : Prominent PHP‑based projects such as Laravel, Symfony, and Composer already use MIT, so a unified core license streamlines collaboration.

Scope and Implementation Details

PHP core code, including the Zend Engine and standard library.

Official extensions such as PDO and MySQLi.

Documentation and example code, which will be re‑licensed accordingly.

Specific changes include:

Removal of the “PHP name usage restriction” and the mandatory retention of the original license for derivative works.

Retention of the original copyright notice (e.g., “Copyright © The PHP Group”) while replacing the license text with the standard MIT terms.

Retroactive application of the new license to all historical commits to avoid mixed‑license complexity.

Community Discussion and Potential Challenges

Historical compatibility : Projects built on the old license (e.g., HHVM) may need to adapt, but the permissive nature of MIT should minimise effort.

Brand protection : Removing the name‑usage clause raises concerns about misuse of the PHP trademark; the proposal suggests handling trademark protection separately, similar to Python or Node.js.

Contributor agreement : Since the PHP Group holds the core copyright, a broad license change does not require individual contributor consent, following common open‑source governance practices.

Long‑Term Significance for the PHP Ecosystem

Adopting a widely accepted permissive license lowers entry barriers, encourages broader adoption by developers and enterprises, and positions PHP for continued relevance in web development, cloud‑native, and embedded contexts.

New PHP Source File Header

/*
   +----------------------------------------------------------------------+
   | Copyright © The PHP Group and Contributors                           |
   +----------------------------------------------------------------------+
   | This source file is subject to the Modified BSD License that is      |
   | bundled with this package in the file LICENSE, and is available    |
   | through the World Wide Web at https://www.php.net/license/.        |
   |                                                                      |
   | SPDX-License-Identifier: BSD-3-Clause                               |
   +----------------------------------------------------------------------+
*/

New Zend Engine Source File Header

/*
   +----------------------------------------------------------------------+
   | Zend Engine                                                         |
   +----------------------------------------------------------------------+
   | Copyright © Zend by Perforce and Contributors                        |
   +----------------------------------------------------------------------+
   | This source file is subject to the Modified BSD License that is      |
   | bundled with this package in the file LICENSE, and is available    |
   | through the World Wide Web at https://www.php.net/license/.        |
   |                                                                      |
   | SPDX-License-Identifier: BSD-3-Clause                               |
   +----------------------------------------------------------------------+
*/