The PHP License is the license under which the reference implementation of the PHP scripting language is released. It is considered a free and open approach to software distribution: it permits users to obtain, modify and redistribute the source for the interpreter while setting out standard conditions such as preservation of notices and disclaimers of warranty. For background on the general concepts, see free software and open source.
Key characteristics
The license focuses on practical permissions for use and redistribution. In broad terms it:
- permits copying, modification and distribution of the implementation;
- requires certain copyright and license notices to be retained in redistributed source;
- includes a disclaimer of warranty and limits liability for the authors and contributors;
- contains clauses addressing how the name "PHP" may be used with derived distributions.
History and development
The license was drafted to govern the distribution of PHP's core source code and has evolved alongside the language. Its terms were developed by the PHP project maintainers to balance the community's ability to modify and redistribute the interpreter with the need to preserve project identity and to limit legal exposure. For the official wording and any version history, consult the license text.
Uses and practical effects
In practice, the PHP License applies to the interpreter and many official extensions. Application code, libraries and frameworks written in PHP are commonly released under a variety of other permissive or copyleft licenses chosen by their authors. Distributors of PHP binaries or source packages must follow the PHP License terms; this affects how vendors package the interpreter and how derivative binaries are named and attributed.
Compatibility and notable facts
The PHP License is broadly recognized as a free/open approach, but its specific naming and redistribution clauses have led to discussions about compatibility with other licenses. Because of those provisions, developers and packagers sometimes evaluate compatibility when combining PHP core components with software under different terms. For information about the language itself and its distribution, see PHP programming language.
Overall, the PHP License plays a central role in how the language's reference implementation is shared and maintained, clarifying rights for users while protecting the project's identity and contributors.