Magento Headers already sent

I have this problem with Headers already sent with Magento. I get this error:

HEADERS ALREADY SENT: 
[0] /var/www/etam/trunk/src/app/code/core/Mage/Core/Controller/Response/Http.php:44
[1] /var/www/etam/trunk/src/lib/Zend/Controller/Resp开发者_如何学编程onse/Abstract.php:727
[2] /var/www/etam/trunk/src/app/code/core/Mage/Core/Controller/Response/Http.php:75
[3] /var/www/etam/trunk/src/app/code/core/Mage/Core/Controller/Varien/Front.php:188
[4] /var/www/etam/trunk/src/app/code/core/Mage/Core/Model/App.php:304
[5] /var/www/etam/trunk/src/app/Mage.php:596
[6] /var/www/etam/trunk/src/index.php:139

I saw this topic but didn't help me much.

I have found that this log I get only when navigating through Admin Panel and going to edit pages with WYSIWYG editor. When in the content of such edit there are .jpg images then I get this headers already sent error.

As far as I discovered it is not for all images but for some of them. For example when there is only 1 image no error then. When there are 3 of them, just for one I get this error.

I can't find any white spaces or unwanted echo nor print. I'm stuck with this and I'm out of ideas what to search for. Maybe you could give me some advices? I know it is harmless, still we don't want to have any errors in system.log.

Sometimes we see "Headers Already Send..." in system.log... to prevent this we should return our data in controllers with one of those methods

clean way:

$this->getResponse()->setBody($response);

or dirty way:

echo $response;

exit();

There are some cases where "clean way" doesn't work, so we must use "dirty way".

Use this if You're getting content via Ajax, like it's done in CMS ;)

Oddly, I created this post just this morning since I ran into a very similar problem when debugging Magento.

http://codemagento.com/2011/03/debugging-headers-already-sent-error/

Alternatively we could overwrite \app\code\core\Mage\Adminhtml\controllers\Cms\WysiwygController.php in the same way Magento 1.9.3 does it. In our case this was changing this part of the function directiveAction()

        try {
        $image = Varien_Image_Adapter::factory('GD2');
        $image->open($url);
        $image->display();
    } catch (Exception $e) {
        $image = Varien_Image_Adapter::factory('GD2');
        $image->open(Mage::getSingleton('cms/wysiwyg_config')->getSkinImagePlaceholderPath());
        $image->display();

to

        try {
        $image = Varien_Image_Adapter::factory('GD2');
        $image->open($url);
    } catch (Exception $e) {
        $image = Varien_Image_Adapter::factory('GD2');
        $image->open(Mage::getSingleton('cms/wysiwyg_config')->getSkinImagePlaceholderPath());
    }
    ob_start();
    $image->display();
    $this->getResponse()->setBody(ob_get_contents());
    ob_end_clean();

Further information (in German) right here. Verified with Magento CE 1.9.2.4.