From experience, everyone knows overriding Magento core functionality can be deadly if not done right. This tutorial gives an example of how to cleanly override core controllers. I’ll use the example of overriding the core contact form’s post-submit action to redirect to a custom thankyou page.
Step 1
First, we need to tell Magento that we have a new module by adding an XML file at /app/etc/module/Dhmedia_Contacts.xml with the following contents: <?xml version="1.0"?><config> <modules> <dhmedia_contacts> <active>true</active> <codepool>local</codepool> <depends> <mage_contacts> </mage_contacts></depends> <version>0.1.0</version> </dhmedia_contacts> </modules> </config> This lets Magento know there is a module in the “local” code pool called Contacts in the Dhmedia namespace (/app/local/Dhmedia/Contacts/...)
Step 2
So now we've told Magento to look for our module, and it does this by trying to find the config.xml file at /app/code/local/Dhmedia/Contacts/etc/config.xml. Create that file with the following contents: <?xml version="1.0"?><config> <modules> <dhmedia_contacts> <version>0.1.0</version> </dhmedia_contacts> </modules> <frontend> <routers> <contacts> <args> <modules> <dhmedia_contacts before="Mage_Contacts">Dhmedia_Contacts</dhmedia_contacts> </modules> </args> </contacts> </routers> </frontend> </config> This file tells Magento to load Dhmedia_Contacts before the core Mage_Contacts. Now any action overrides in our local module will take priority over the core functionality.
Step 3
Now that Magento knows where to find our module and which modules we're rewriting, we need to provide new behavior. In this example, we override the default contact post action by extending Mage_Contacts_IndexController with our own class, Dhmedia_Contacts_IndexController. Do this by creating /app/code/local/Dhmedia/Contacts/controllers/IndexController.php with the following contents: <?php
include_once "Mage/Contacts/controllers/IndexController.php";
class Dhmedia_Contacts_IndexController extends Mage_Contacts_IndexController
{
public function postAction()
{
parent::postAction();
$this->_redirect('thankyou');
}
}
?>If you can follow the flow of execution, Magento will call our postAction method when a form is submitted. Our method calls the parent’s post action to invoke the core behavior so we don’t need to copy any core code into our module. Next we tell Magento to redirect to the ‘thankyou’ page. Assuming you have created a CMS page in the admin backend with ‘thankyou’ as its URL alias, the task of overriding the default post redirect in an upgrade-proof way is complete.
The potential is limitless
You can use these same techniques to override pretty much any core Magento controller’s actions, or even to define your own actions. This is a very powerful technique and very poorly documented, so I hope this post has been of some use to somebody. This information should be correct as of version 1.4.1.1 and is hopefully good for another couple of major revisions.
