PHP License Retired: What You Need to Know About the Shift to BSD

The PHP project has undergone a significant licensing change. After decades under its own PHP License (alongside the Zend Engine License for certain components), the project has officially retired the PHP License and now uses the permissive three-clause BSD license. This transition was not a simple decision—it required extensive legal review, community discussion, and approvals from key stakeholders. Below, we explore the details of this process and what it means for the PHP ecosystem.

What was the original licensing structure for PHP?

For many years, PHP was distributed under its own PHP License, with the exception of the Zend Engine components which were licensed under the Zend Engine License. The PHP License was a custom license created by the PHP Group, designed specifically for the PHP project. While it was generally considered open source, its uniqueness sometimes caused confusion or compatibility issues with other open source licenses. The Zend Engine License, meanwhile, was used for the core engine code originally developed by Zend Technologies.

Why did the PHP project decide to retire its own license?

The primary motivation was to simplify licensing and improve compatibility with the broader open source ecosystem. The PHP License was not widely used outside the project, and its terms occasionally created friction when combining PHP with software under more common licenses like the MIT or BSD licenses. By moving to the three-clause BSD license—a well-known, permissive license—PHP reduces legal barriers for developers and distributors. This change also aligns PHP with many other popular open source projects, fostering easier collaboration and integration.

What is the new license for PHP, and why was it chosen?

The PHP project has chosen the three-clause BSD license as its new license. This license is permissive, allowing anyone to use, modify, and distribute the software with minimal restrictions. The three clauses require that copyright notices and disclaimers be preserved, and that the names of contributors not be used for endorsement without permission. It was selected because it is simple, widely recognized, and compatible with most other open source licenses. This eliminates the need for dual-licensing or special exceptions that the old PHP License sometimes required.

Who had to approve the license change?

Approval required consent from two key groups. First, all original PHP Group members needed to give written permission because the PHP License granted them authority to modify terms. Each member was located and signed off on the proposal. Second, Perforce Software, the successor to Zend Technologies, had to approve for the Zend Engine portions. Perforce provided a formal letter confirming their full authority and support. Additionally, an attorney was hired to review the proposal and advise on legal questions, ensuring the transition was sound from a legal perspective.

How was the community involved in this decision?

Community engagement was an essential part of the process. The PHP project allowed for a six-month discussion period before any vote took place. During this time, developers, users, and other stakeholders could raise concerns, ask questions, and provide feedback. Following the discussion, a formal vote was conducted. The result was a unanimous decision in favor of relicensing under the three-clause BSD license. This open, transparent approach ensured that the community had a voice in a change that affects every PHP user.

How long did the entire license change process take?

The process stretched over several months. After initial planning and legal review, the community discussion period itself lasted six months. Prior to that, obtaining written consent from each original PHP Group member required time and effort. Working with Perforce Software and the attorney also added to the timeline. The final vote passed unanimously, marking the end of a thorough, careful process. Through this, the PHP project demonstrated its commitment to due diligence and community governance, setting a precedent for how license changes can be handled in open source projects.