Re: [RFC] Readonly Variables

On Tue, 24 Feb 2026 at 19:32, Larry Garfield <larry@garfieldtech.com> wrote: > > On Tue, Feb 24, 2026, at 12:52 PM, Joshua Rüsweg wrote: > > >> I would prefer starting with readonly parameters as I feel that would > >> bring the most value. > > > > I find the idea of readonly parameters interesting and have already > > given it some thought. However, it is out of scope for this RFC, as I > > wanted to keep the initial proposal focused and manageable. I have > > already mentioned it in the Future Scope section of the RFC as a > > potential natural extension that could be addressed in a separate RFC > > in the future. > > A slight tangent here, but what would readonly parameters do? > > If you pass something by value, then already you cannot modify the value in the caller. If the > value is large, it's already kept efficient by copy-on-write. > > If you pass by reference, then presumably you *want* to modify the value in the caller. > > If the value is an object, then as already discussed, its internals are mutable either way so > you gain little, but the function cannot change the identity in the caller anyway. > > So I don't see what readonly parameters would even accomplish. The thing they accomplish > in JS or Java or C simply doesn't apply in PHP. > > I'm still undecided at the moment on readonly variables. > > --Larry Garfield A readonly parameter would mean that it would be impossible to reuse the variable within the function for something else. It's not uncommon for a function to preprocess the argument and still make use of the original value. A readonly modifier would prevent accidental overwrite. function foo(string|array $data) { if (is_string($data) ) { $data = [$data]; // Original argument lost } // .... return is_string($data) ? $result : [$result]; )