Magento – Magento 2 : How to get success/error message after review post

Try to give your div-container a css-class:

<div id="messages_product_view" class="test1"><?php Mage::app()->getLayout()->getMessagesBlock()->setMessages(Mage::getSingleton('customer/session')->getMessages(true)); ?> <?php echo Mage::app()->getLayout()->getMessagesBlock()->getGroupedHtml(); ?> </div>

And then you define this class in your css-file:

.test1 {z-index: 99999;}

I'm not shure if it works, but on our website it is solved so.

For ajax calls you need to return the error messages if any. It does not work with $session->addError(). The message you set with addError are picked up on the next page load.

You need to do something like this in your controller:

public function doSomeAjaxStuff()
{
    $response = array();
    $response['success'] = true;
    //do stuff here
    $response['something'] = 'Something';
    if (some error occurs) {
        $response['success'] = false;
        $response['message'] = 'Your error message here';
    }
    $this->getResponse()->setBody(Mage::helper('core')->jsonEncode($response); 
}

And in your javascript code that handles the response from the ajax call do this:

if (!response.success) {
    alert(response.message);
    //or insert response.message somewhere in the dom
}