A PHP internals RFC discussion proposes adding literal scalar types to PHP, allowing function signatures to express exact accepted values like `0|1|2` or `"ascii"|"utf-8"` as types. The RFC author argues this fills gaps that enums cannot: retrofitting existing scalar APIs without breaking callers, defining open value sets that can grow without BC breaks, and enabling direct scalar interop (array keys, JSON, strict equality). A community member counters that enums already cover most use cases, questioning whether the scope of change is justified, and arguing backed enums handle scalar interop through value exposure.
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