A PHP internals mailing list discussion around a new RFC proposing literal scalar types for PHP. The RFC would allow function signatures to express exact scalar values as types, e.g. `function check(-1|0|1 $x): void {}`. The author argues this fills gaps that enums cannot: retrofitting existing scalar APIs without breaking callers, ad-hoc open value sets that can grow without BC breaks, and native scalar interop (array keys, JSON, strict equality). Community members debate whether enums already cover these cases, raise questions about constant references and enum values in type positions (both out of scope), and discuss mixing literal types with wider types in unions (supported by design). A range syntax like `-1..1` is acknowledged as a logical follow-up but intentionally excluded from this RFC. An alternative approach via pattern matching parameter guards is also mentioned.
