PSRs (PHP Standard Recommendations) er et sæt standarder udgivet af PHP-FIG (Framework Interoperability Group), der definerer almindelige konventioner — kodestil, autoloading og delte interfaces — som muliggør interoperabilitet mellem forskellige PHP-frameworks, biblioteker og pakker.
De vigtigste PSR'er
PSR-1 / PSR-12 → CODING STYLE (basic + extended): naming, braces, indentation, etc.
PSR-4 → AUTOLOADING: namespace ↔ directory mapping (used by Composer)
PSR-3 → LoggerInterface: a common logging interface
PSR-7 → HTTP message interfaces (Request/Response objects)
PSR-11 → ContainerInterface: a common DI container interface
PSR-15 → HTTP middleware interface
PSR-6 / PSR-16 → Caching interfaces
PSR-18 → HTTP client interface
