I'm running Magento and whenever I try to delete a product I get an HTTP ERROR 500 page. Everything else seems to work normally.

The error log says:

PHP Fatal error: Call to a member function joinRel() on boolean in /home/xxxxxxxx/public_html/app/code/core/Mage/Tag/Model/Tag.php on line 127

This is the relevant section from that tag.php file:

    protected function _getProductEventTagsCollection(Varien_Event_Observer $observer)
    return $this->getResourceCollection()

I can't find any reference to this online at all and I'm completely stumped. Has anyone got any ideas, or suggest a fix?

Many thanks.

  • I'm not familiar with this error. Apparently $this->getResourceCollection() returns false. Just to be sure, did you try to clean the cache and reindex?
    – Niels
    Jul 20, 2017 at 9:05
  • Yes, have cleared cache numerous times and re-indexed. No difference.
    – Alan C
    Jul 20, 2017 at 11:58
  • OK, very strange indeed. Did you recently activate or install any new modules that might have changed the behavior?
    – Niels
    Jul 20, 2017 at 12:20
  • I had recently installed a social media button extension and changed the DNS to run through Cloudflare. I have now uninstalled that extension and changed the DNS back the way it was and no difference. Is it possible that an extension could make a permanent change? I may have to try loading backups onto a test site to see when this probem started.
    – Alan C
    Jul 20, 2017 at 22:07
  • I have loaded a backup onto a test site from July 2 (pre the social media button extension) and it does delete products correctly. So it seems that the extension has created a persistant issue somehow. Thanks for your time. I will have to roll back.
    – Alan C
    Jul 21, 2017 at 0:42

1 Answer 1


Apparently $this->getResourceCollection() returns false.

If you look at the code in app/code/core/Mage/Core/Model/Abstract.php, you can see that it tries to load a resource collection for a specified _resourceCollectionName:

public function getResourceCollection()
        if (empty($this->_resourceCollectionName)) {
            Mage::throwException(Mage::helper('core')->__('Model collection resource name is not defined.'));
        return Mage::getResourceModel($this->_resourceCollectionName, $this->_getResource());

Did you see anything in the error logs? Is the Exception thrown for example (/var/log/exception.log by default)? Look like Magento tries to load a resource Collection model that is somehow not defined.

  • The only thing in the exception.log file is a lot of repeated errors for invalid block type. - 'Mage_Core_Exception' with message 'Invalid block type: ' in /home/xxxxxxxx/public_html/app/Mage.php:595. Pretty sure that this is a separate problem that I'm also going to have to sort out.
    – Alan C
    Jul 20, 2017 at 22:19
  • 1
    Problem solved - it was an extension that was causing the issue.
    – Alan C
    Jul 21, 2017 at 0:47

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