Naming conventions for code released by PHP FIG

1. Interfaces MUST be suffixed by Interface: e.g. Psr\Foo\BarInterface.
2. Abstract classes MUST be prefixed by Abstract: e.g. Psr\Foo\AbstractBar.
3. Traits MUST be suffixed by Trait: e.g. Psr\Foo\BarTrait.
4. PSR-1, 2 and 4 MUST be followed.
5. The vendor namespace MUST be Psr.
6. There MUST be a package/second-level namespace in relation with the PSR that
   covers the code.
7. Composer package MUST be named psr/<package> e.g. psr/log. If they
   require an implementation as a virtual package it MUST be named
   psr/<package>-implementation and be required with a specific version like
   1.0.0. Implementors of that PSR can then provide
   "psr/<package>-implementation": "1.0.0" in their package to satisfy that
   requirement. Specification changes via further PSRs should only lead to a new
   tag of the psr/<package> package, and an equal version bump of the
   implementation being required.
8. Special lighweight utility packages MAY be produced alongside PSRs and
   interfaces and be maintained and updated after the PSR has been accepted. These
   MUST be under the vendor namespace Fig.