Fix ‘Namespace_Module_Helper_Data’ not found fatal error in Magento ?

Following are the steps to resolve”fatal error: Class ‘Namespace_Module_Helper_Data’ not found” error.

  1. Install the extension when compilation is disabled in Magento admin.
  2. To check whether compilation is enabled or disabled, go to
    Admin > system >Tools > compilation  check enabled / disabled
  3. If enabled, then disable it and install the extension. Once the extension is installed you can enable compilation again by using ‘Re-run Compilation.
  4. If you have already installed the extension & are facing the above error, Disable the extension from app/etc/modules/Namespace_Module.xml
  5. <active>true</active> 
  6. Clear cache from var/cache folder.
  7. Now you will have the access to Magento admin panel from where you can disable the compilation.
  8. Now enable the extension from Namespace_Module.xml
  9. <active>false</active>
  10. Clear cache from var/cache folder.