Question

I know how to override Mage classes (any class within app/code/core)
My question is how to override Varien classes? (classes within lib/Varien)

If I want to override Mage_Adminhtml_Block_Page_Menu
I create a class MyCompany_Adminhtml_Block_Page_Menu under app/code/local/MyCompany/Adminhtml/Block/Page/Menu.php

I name it like:

 class MyCompany_Adminhtml_Block_Page_Menu extends Mage_Adminhtml_Block_Page_Menu

Now Magento uses my class MyCompany_Adminhtml_Block_Page_Menu instead of Mage_Adminhtml_Block_Page_Menu

My question is: where should I put the new class, and how to name it, to override, for example Varien_Date (lib/Varien/Date.php)

Thanks

Answer 1

If you must, copy the file and path to the local codepool and make the necessary changes. There is no configuration mapping to change the class name.

Explanation: see the bootstrapping in app/Mage.php. There is a load order set for the codepools and libraries in the following order:

1. app/code/local/
2. app/code/community/
3. app/code/core/
4. lib/

Typically, Varien_Autoload is responsible for mapping classnames such as Varien_Data_Collection_Db, Mage_Core_Model_Abstract, or Zend_Db_Select to relative filenames (Varien/Data/Collection/Db.php, Mage/Core/Model/Abstract.php, and Zend/Db/Select.php respectively). These file locations are then passed to include(), which internally uses the load order set in the bootstrap. Therefore, if the file Varien/Data/Collection/Db.php is present under one of the “earlier” locations, that version of the class definition will be used.

These type of modifications may be justified, but they should be well-considered and documented, as the entire definition will be owned by you and any upgrades will need to be merged in the future. It would be good to know what you would like to change, as someone else may have a slightly less invasive option.