PSR

PSR refers to PHP Standards Recommendations, a set of coding and interface standards for PHP developed and maintained by the PHP Framework Interop Group (PHP-FIG). The intent of PSRs is to promote interoperability among PHP libraries and applications by establishing common conventions that developers can follow across projects. PSRs are voluntary and are adopted by projects to improve consistency, portability, and collaboration.

PSRs are proposed and discussed within the PHP-FIG, and, once accepted, published as formal recommendations with numerical identifiers such as PSR-1, PSR-2, PSR-4, PSR-7, and others. The standards cover a range of topics, including coding style (PSR-1, PSR-12; with PSR-12 superseding PSR-2), autoloading (PSR-4, replacing PSR-0), and common interfaces for cross-cutting concerns such as logging (PSR-3), HTTP messages (PSR-7), dependency containers (PSR-11), and HTTP server request handling (PSR-15).

Adoption and impact: PSRs have become widely influential in the PHP ecosystem. Many frameworks, libraries, and tools aim to be PSR-compliant to facilitate integration and reuse. Composer, the prevalent PHP package manager, often relies on PSR-based autoloading and interfaces. Critics note that PSRs vary in scope and may not cover all use cases, leading some projects to adopt only a subset or blend PSR guidelines with project-specific conventions.

See also: PHP-FIG, PHP standards.