Fix #18394: Add support for setting `yii\web\Response::$stream` to a callable

framework/CHANGELOG.md

@@ -4,7 +4,7 @@ Yii Framework 2 Change Log
 2.0.40 under development
 ------------------------
 
-- no changes in this release.
+- Enh #18394: Add support for setting `yii\web\Response::$stream` to a callable (brandonkelly)
 
 
 2.0.39.3 November 23, 2020

framework/web/Response.php

@@ -138,9 +138,12 @@ class Response extends \yii\base\Response
      */
     public $content;
     /**
-     * @var resource|array the stream to be sent. This can be a stream handle or an array of stream handle,
-     * the begin position and the end position. Note that when this property is set, the [[data]] and [[content]]
-     * properties will be ignored by [[send()]].
+     * @var resource|array|callable the stream to be sent. This can be a stream handle or an array of stream handle,
+     * the begin position and the end position. Alternatively it can be set to a callable, which returns
+     * (or [yields](https://www.php.net/manual/en/language.generators.syntax.php)) an array of strings that should
+     * be echoed and flushed out one by one.
+     *
+     * Note that when this property is set, the [[data]] and [[content]] properties will be ignored by [[send()]].
      */
     public $stream;
     /**
@@ -441,6 +444,15 @@ class Response extends \yii\base\Response
             Yii::warning('set_time_limit() is not available', __METHOD__);
         }
 
+        if (is_callable($this->stream)) {
+            $data = call_user_func($this->stream);
+            foreach ($data as $datum) {
+                echo $datum;
+                flush();
+            }
+            return;
+        }
+
         $chunkSize = 8 * 1024 * 1024; // 8MB per chunk
 
         if (is_array($this->stream)) {