Was trying to create an admin module and got the helper_class not found error

Fatal error: Class 'my_module_Helper_Data' not found in /home/myweb/public_html/app/Mage.php on line 547

But now I can't access admin panel after deleting the files I uploaded including the app/etc/modules/my_module.xml.

Tried emptying var/cache but still no luck :/!

3 Answers 3


Weirdest bug I've encountered and just to be clear it was a cache issue and this is how I resolved it:

class my_module_Helper_Data extends Mage_Core_Helper_Abstract


added this code to the bottom of core Mage.php, logged into admin and refreshed cache then removed it back off the bottom of the core Mage.php.

  • What isthe general file path to get to the Mage.php file? Dec 7, 2016 at 20:21
  • 1
    I accessed it trough admin panel it was invisible to my text editor! THANK YOU FOR THIS it saved my ass Dec 7, 2016 at 21:10
  • glad it helped :) Dec 8, 2016 at 9:03

Your helper is definitely referenced somewhere.

If disabling the module by setting active to false in the app/etc/modules/my_module.xml file does not work, that means the helper is referenced in a file which is not related to the module (template for instance).

  • No it's not I had a folder all to itself so I removed all the files it added so I could revert with no worries. Jan 19, 2016 at 11:12
  • (locally that is) Jan 19, 2016 at 11:12
  • Do you have compilation enabled ? Could you post your module config.xml file ? Jan 19, 2016 at 11:14
  • Don't have compilation enabled, the module 100% is not referenced anywhere else, it was when I refreshed the cache it happened Jan 19, 2016 at 11:16
  • and since the module's config isn't even on the server anymore what difference would it make? Jan 19, 2016 at 11:16

Open file [MAGENTO_ROOT]/includes/config.php


Change these to following


Hope it helps you

  • they are already commented Jan 19, 2016 at 11:15
  • Check it by disabling local modules from app/etc/local.xml. Jan 19, 2016 at 11:22
  • did that and still same thing Jan 19, 2016 at 11:25
  • its definitely a caching issue just don't understand why it's not clearing cache, double checked ftp details etc about 20 times lol Jan 19, 2016 at 11:25
  • Check manually deleting var/cache directory Jan 19, 2016 at 11:28

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