Fix issue where overwriting middleware variable when setting middleware priority (#53504)

Author: ollieread

src/Illuminate/Foundation/Configuration/ApplicationBuilder.php

@@ -271,14 +271,14 @@ public function withMiddleware(?callable $callback = null)
             }
 
             if ($priorityAppends = $middleware->getMiddlewarePriorityAppends()) {
-                foreach ($priorityAppends as $middleware => $after) {
-                    $kernel->addToMiddlewarePriorityAfter($after, $middleware);
+                foreach ($priorityAppends as $newMiddleware => $after) {
+                    $kernel->addToMiddlewarePriorityAfter($after, $newMiddleware);
                 }
             }
 
             if ($priorityPrepends = $middleware->getMiddlewarePriorityPrepends()) {
-                foreach ($priorityPrepends as $middleware => $before) {
-                    $kernel->addToMiddlewarePriorityBefore($before, $middleware);
+                foreach ($priorityPrepends as $newMiddleware => $before) {
+                    $kernel->addToMiddlewarePriorityBefore($before, $newMiddleware);
                 }
             }
         });