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Date: Sun, 18 Jan 2026 14:07:02 +0100
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Subject: Re: [PHP-DEV] [RFC] Context Managers
To: Volker Dusch <edorian@php.net>, Larry Garfield <larry@garfieldtech.com>
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

On 1/15/26 19:38, Volker Dusch wrote:
> a function is already a reasonable scope

That - together with the other points you raised - made me realize one 
thing: In contrast to block scoping, the main purpose of “Context 
Managers” is *not* managing arbitrary variables in the current scope in 
combination with existing control structures. Instead it is just 
managing a single variable in a reasonably *self-contained* fashion, 
with other variables just needing to “exist”.

It could therefore also just be a regular function taking a callback, as 
is already done in userland, e.g. with Laravel's DB::transaction() helper.

I believe something like this would be equivalent to the RFC:

     function using(
         callable $runInContext,
         ContextManager ...$managers
     ): void {
         $contexts = [];
         foreach ($managers as $manager) {
             $contexts[] = $manager->enterContext();
         }

         try {
             $runInContext(...$contexts);
             foreach (array_reverse($managers) as $manager) {
                 $manager->exitContext();
             }
         } catch (Throwable $e) {
             foreach (array_reverse($managers) as $manager) {
                 if ($manager->exitContext($e) === true) {
                     $e = null;
                 }
             }
             if ($e !== null) {
                 throw $e;
             }
         }
     }

This would completely side-steps the “break to exit” question, since a 
`return` will just work. It also avoids introducing new keywords, it 
just requires a new function in the global namespace.

I understand that using variables from the current scope in a Closure is 
currently not particularly convenient, particularly when they need to be 
changed. However this is something that can be solved in a generic 
fashion, for example inspired by the C++ lambda syntax:

     // Captures everything by value and $result by reference.
     function ($context) use (*, &$result) { }

     // Captures everything by reference.
     function ($context) use (&*) { }

which would also be useful in other situations.

Best regards
Tim Düsterhus