---
title: "[RFC] [Discussion] Literal Scalar Types"
url: https://daily.dev/posts/rfc-discussion-literal-scalar-types-qztvubl0q
source_url: https://externals.io/message/131582
type: article
source: "externals.io"
published: 2026-06-29T11:58:37.509Z
updated: 2026-06-29T11:59:04.664Z
tags: ["php"]
reading_time: 47
upvotes: 0
comments: 0
language: en
---

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# [RFC] [Discussion] Literal Scalar Types

**[externals.io](https://daily.dev/sources/externals)** · 47 min read · 0 upvotes · 0 comments

## Summary

A PHP internals mailing list discussion around a proposed RFC to add literal scalar types to PHP, allowing function signatures to express exact allowed values like `0|1|2` or `'success'|'error'`. The RFC author argues literal types fill gaps that enums cannot: describing existing scalar APIs without breaking callers, ad-hoc open value sets that can grow without BC breaks, and direct scalar interop (JSON round-trips, array keys, === comparisons with raw values). Skeptics counter that enums already handle most cases through backed enum values and a gradual migration path, and that literal types in signatures produce poor error messages. The discussion converges on a complementary view: enums for named, reusable, behaviour-carrying sets; literal types for raw scalar data like decoded JSON payloads and discriminated unions on the wire.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://externals.io/message/131582>

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