Move category

$category = Mage::getModel('catalog/category')->load($idCategoryForMoving);
$category->move($idParentCategory, $idAfterCategory);

Getting filterable attributes in category

Getting filterable attributes from layered navigation

$category = Mage::registry('current_category');
$products = $category->getProductCollection();

$appliedFilters = Mage::getSingleton('catalog/layer')->getFilterableAttributes();
foreach ($appliedFilters as $filter) {
  if ($value = $this->getRequest()->getParam($filter->getAttributeCode())) {
      $products->addFieldToFilter($filter->getAttributeCode(), $value);
  }
}

Method getFilterableAttributes returns all available attributes for filtering. Then in foreach we check if an attribute has been selected by user, we add it to the filter.

Increase the size of a VDI file

You can only increase size

VBoxManage modifyhd YourFile.vdi --resize 32240

Include third party libraries

For including third party libraries from lib folder

require_once(Mage::getBaseDir('lib') . '/simple_html_dom.php');

Determine page type in magento

For category page (in layout xml file):

 
  
   category
  
 

And in your block class you can get value of page type:

$this->setPageType()

For other pages you can do the same - just replace catalog_category_view with your action.

Add column in magento install/upgrade script

For adding a new column to table in magento installer you have to add to your install/upgrade script:

$installer = $this;
$installer->startSetup();
// ...
$installer->getConnection()->addColumn(
    $this->getTable('sales/quote_payment'),
    'billing_code', // column name
    'VARCHAR(255) NOT NULL' // type definition
);
// ...
$installer->endSetup();

Rewrite controllers in magento

For rewriting controller in magento you have to add to your module config.xml:

 
  
   
    
     SliRx_Test
    
   
  
 

where Mage_Checkout - module with a controller which you are going to rewrite.
SliRx_Test - your module which contains the controller for rewrite.

The above config means that magento will search the controller in your module first and after that, if doesn't find it, in Mage_Checkout.
Then you have to create the file SliRx/Test/controllers/CartController.php:

require_once(Mage::getModuleDir('controllers', 'Mage_Checkout') . DS . 'CartController.php');

class SliRx_Test_CartController extends Mage_Checkout_CartController
{
    public function indexAction()
    {
        echo "it's cart!";
    }
}

But magento doesn't know about Mage_Checkout_CartController and you must include the file with this class by yourself. That's why before declaring SliRx_Test_CartController calls require_once;