minor #49763 Replace "use-by-ref" by static vars when possible in closures (nicolas-grekas)

This PR was merged into the 6.3 branch.

Discussion
----------

Replace "use-by-ref" by static vars when possible in closures

| Q             | A
| ------------- | ---
| Branch?       | 6.3
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

Might be easier to grasp.

Commits
-------

65422ecf4b Replace "use-by-ref" by static vars when possible in closures

Author: nicolas-grekas

AcceptHeader.php

@@ -46,11 +46,10 @@ public function __construct(array $items)
      */
     public static function fromString(?string $headerValue): self
     {
-        $index = 0;
-
         $parts = HeaderUtils::split($headerValue ?? '', ',;=');
 
-        return new self(array_map(function ($subParts) use (&$index) {
+        return new self(array_map(function ($subParts) {
+            static $index = 0;
             $part = array_shift($subParts);
             $attributes = HeaderUtils::combine($subParts);