Sometimes we may need to override a method or add functionality in a controller of Magento.

We are going to assume that you already have a local extension.

In this case, we are going to override the saveAction() method of the Mage_Adminhtml_Sales_Order_InvoiceController located into app/code/core/Mage/Adminhtml/controllers/Sales/Order/InvoiceController.php.

To do so, let’s perform the following steps:

• app/code/local/Offset101/OverrideController/etc/config.xml
  
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  <?xml version="1.0"?> <config>    <modules>        <Offset101_OverrideController>            <version>0.0.1</version>        </Offset101_OverrideController>    </modules>     <admin>         <routers>             <adminhtml>                 <use>admin</use>                 <args>                     <modules>                         <offset101_overridecontroller before="Mage_Adminhtml">Offset101_OverrideController_Adminhtml</offset101_overridecontroller>                     </modules>                 </args>             </adminhtml>         </routers>     </admin> </config>

  
   

  <admin>  Is where we are going to override the route (it could be frontend or global instead).
  <routers> Is what we are going to add in our local extension.
  <adminhtml> Is whichever extension we want to override, in this case is Adminhtml and the vendor is Mage.
  offset101_overridecontroller  Is the identifier of our local extension.
  before=”Mage_Adminhtml” Is the overriden controller.
  Offset101_OverrideController_Adminhtml is Vendor_Modulename_Adminhtml just because we are overriding an adminhtml controller( it should be Offset101_OverrideController in case we want to override a frontend controller).

• app/code/local/Offset101/OverrideExtension/controllers/Adminhtml/Sales/Order/InvoiceController.php
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  <?php // We should add a require for the overriden class. require_once(Mage::getModuleDir('controllers','Mage_Adminhtml').DS."Sales".DS."Order".DS."InvoiceController.php"); class Offset101_OverrideController_Adminhtml_Sales_Order_InvoiceController extends Mage_Adminhtml_Sales_Order_InvoiceController {     public function saveAction()     {       Mage::log('Hello overriden method !');     } }

  Then remember to clean cache, and make a try!

In case that we need to override a frontend controller, we will need to proceed as follows (ie: to override the customer account create controller):

• app/code/local/Offset101/OverrideController/etc/config.xml
  
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  <?xml version="1.0"?> <config>    <modules>        <Offset101_OverrideController>            <version>0.0.1</version>        </Offset101_OverrideController>    </modules>     <frontend>        <customer>             <args>                 <modules>                     <offset101_overridecontroller before="Mage_Customer">Offset101_Customers</offset101_overridecontroller>                 </modules>              </args>        </customer>     </frontend> </config>

• app/code/local/Offset101/OverrideExtension/controllers/AccountController.php
  
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  <?php include_once('Mage/Customer/controllers/AccountController.php');   class Offset101_Customers_AccountController extends Mage_Customer_AccountController {       /**      * Customer register form page      */     public function createAction()     {         Mage::log('Hello overriden method !');         return;     }   }

  
  Then remember to clean cache, and make a try!