@phpstan-pure

The @phpstan-pure tag declares a function or method as pure — free of side effects, always returning the same result for the same arguments. It is defined by the static analyzer PHPStan.

Parsing a @phpstan-pure tag produces a PureTag instance. Being a pure marker, it adds nothing beyond the $name and optional $description every Tag already carries.

The same PureTag is produced by @psalm-pure and @phan-pure, which restate the same concept for their respective tools.

See PHPStan's PHPDoc basics.