A number of type names were already soft-reserved for PHP 7, which means that we reserve the right to introduce these in a minor release and as such strongly discourage their use, however no actual error or warning will be thrown if they are used against this recommendation. This RFC proposes a number of additional soft reservations, which have been previously missed.
Each of the proposed reservations is listed separately in the following. Votes will also happen separately. This RFC is open to additional suggestions.
All reservations are case-insensitive.
Where: As the last segment of a class, interface or trait name. As such the names Void and Foo\Bar\Void are reserved, while Foo\Bar\MyVoid and Void\Foo\Bar are okay.
Why: void is a likely candidate for the demarcation of void functions (which do not return a value). Alternatively null can be used for this purpose, which is already reserved. However both possibilities should be kept open until we reach a decision on this question.
Where: In any context which is not protected by the context sensitivity RFC. This includes any segment of class, interface, trait and function names.
Why: There already is an enum RFC which will be proposed for PHP 7.x and requires this reserved keyword.
Code using the aforementioned names (in the relevant contexts) should be changed to use a different name. However this is not strictly required.
Votes will be per name and require 2/3 majority.