added ability to convert the response body

flight/net/Response.php

@@ -128,6 +128,13 @@ class Response
      */
     protected bool $sent = false;
 
+    /**
+     * These are callbacks that can process the response body before it's sent
+     *
+     * @var array<int, callable> $responseBodyCallbacks
+     */
+    protected array $responseBodyCallbacks = [];
+
     /**
      * Sets the HTTP status of the response.
      *
@@ -429,8 +436,37 @@ class Response
             $this->sendHeaders(); // @codeCoverageIgnore
         }
 
+        // Only for the v3 output buffering.
+        if($this->v2_output_buffering === false) {
+            $this->processResponseCallbacks();
+        }
+
         echo $this->body;
 
         $this->sent = true;
     }
+
+    /**
+     * Adds a callback to process the response body before it's sent. These are processed in the order
+     * they are added
+     *
+     * @param callable $callback The callback to process the response body
+     * @return void
+     */
+    public function addResponseBodyCallback(callable $callback): void
+    {
+        $this->responseBodyCallbacks[] = $callback;
+    }
+
+    /**
+     * Cycles through the response body callbacks and processes them in order
+     *
+     * @return void
+     */
+    protected function processResponseCallbacks(): void
+    {
+        foreach ($this->responseBodyCallbacks as $callback) {
+            $this->body = $callback($this->body);
+        }
+    }
 }

tests/ResponseTest.php

@@ -255,4 +255,37 @@ class ResponseTest extends TestCase
         $response->write('new', true);
         $this->assertEquals('new', $response->getBody());
     }
+
+    public function testResponseBodyCallback()
+    {
+        $response = new Response();
+        $response->write('test');
+        $str_rot13 = function ($body) {
+            return str_rot13($body);
+        };
+        $response->addResponseBodyCallback($str_rot13);
+        ob_start();
+        $response->send();
+        $rot13_body = ob_get_clean();
+        $this->assertEquals('grfg', $rot13_body);
+    }
+
+    public function testResponseBodyCallbackMultiple()
+    {
+        $response = new Response();
+        $response->write('test');
+        $str_rot13 = function ($body) {
+            return str_rot13($body);
+        };
+        $str_replace = function ($body) {
+            return str_replace('g', 'G', $body);
+        };
+        $response->addResponseBodyCallback($str_rot13);
+        $response->addResponseBodyCallback($str_replace);
+        $response->addResponseBodyCallback($str_rot13);
+        ob_start();
+        $response->send();
+        $rot13_body = ob_get_clean();
+        $this->assertEquals('TesT', $rot13_body);
+    }
 }