Imagick image can not be converted to string on HHVM

framework/CHANGELOG.md

@@ -55,6 +55,7 @@ Yii Framework 2 Change Log
 - Bug: Fixed inconsistent return of `\yii\console\Application::runAction()` (samdark)
 - Bug: URL encoding for the route parameter added to `\yii\web\UrlManager` (klimov-paul)
 - Bug: Fixed the bug that requesting protected or private action methods would cause 500 error instead of 404 (qiangxue)
+- Bug: Fixed Object of class Imagick could not be converted to string in CaptchaAction (eXprojects, cebe)
 - Enh #2264: `CookieCollection::has()` will return false for expired or removed cookies (qiangxue)
 - Enh #2435: `yii\db\IntegrityException` is now thrown on database integrity errors instead of general `yii\db\Exception` (samdark)
 - Enh #2837: Error page now shows arguments in stack trace method calls (samdark)

framework/captcha/CaptchaAction.php

@@ -247,7 +247,7 @@ class CaptchaAction extends Action
     /**
      * Renders the CAPTCHA image based on the code using GD library.
      * @param string $code the verification code
-     * @return string image contents
+     * @return string image contents in PNG format.
      */
     protected function renderImageByGD($code)
     {
@@ -300,7 +300,7 @@ class CaptchaAction extends Action
     /**
      * Renders the CAPTCHA image based on the code using ImageMagick library.
      * @param string $code the verification code
-     * @return \Imagick image instance. Can be used as string. In this case it will contain image contents.
+     * @return string image contents in PNG format.
      */
     protected function renderImageByImagick($code)
     {
@@ -332,8 +332,7 @@ class CaptchaAction extends Action
         }
 
         $image->setImageFormat('png');
-
-        return $image;
+        return $image->getImageBlob();
     }
 
     /**