Part of PSR-0 is a standard for autoloading namespaced classes, so, if you write you're own autoloader, implementing PSR-0 is neccessary to support loading libr

Part of PSR-0 is a standard for autoloading namespaced classes, so, if you write you're own autoloader, implementing PSR-0 is neccessary to support loading libraries using that standard. The situation before PSR-0 was a mess of different, incompatible directory layouts for loadable libraries.