Programmatically: How to create custom Magento admin grids

Step 1: Create a new module with etc/module.xml file

Create a new directory MyCompany/MyModule and add the following etc/module.xml file:

	<?xml version="1.0"?>
	<config>
		<modules>
			<MyCompany_MyModule>
				<version>1.0.0</version>
			</MyCompany_MyModule>
		</modules>
	</config>
	

Step 2: Define the grid in etc/adminhtml/grid.xml file

Create a new directory app/code/local/MyCompany/MyModule/etc/adminhtml and add the following grid.xml file:

	<?xml version="1.0"?>
	<config>
		<adminhtml>
			<grid>
				<my_custom_grid translate="label">
					<label>My Custom Grid</label>
					<classes>
						<name>MyCompany_MyModule::grid/my_custom_grid</name>
					</classes>
				</my_custom_grid>
			</grid>
		</adminhtml>
	</config>
	

Step 3: Create a new PHP class that extends Mage_Adminhtml_Block_Widget_Grid and overrides the prepareCollection() and addMassaction() methods

Create a new directory app/code/local/MyCompany/MyModule/Block/Adminhtml and add the following PHP class:

	class MyCompany_MyModule_Block_Adminhtml_Grid_MyCustomGrid extends Mage_Adminhtml_Block_Widget_Grid
  {
    public function __construct()
    {
        parent::__construct();
        $this->setId('my_custom_grid');
        $this->setDefaultSort('id');
        $this->setDefaultDir('ASC');
        $this->setSaveParametersInSession(true);
    }

    protected function _prepareCollection()
    {
        $collection = Mage::getModel('mycompany_mymodule/my_model')->getCollection();
        $this->setCollection($collection);
        return parent::_prepareCollection();
    }

    protected function _addMassaction()
    {
        if (!Mage::app()->isSingleStoreMode()) {
            $this->getMassactionBlock()->addItem('delete', array(
                'label' => Mage::helper('adminhtml')->__('Delete'),
                'url' => $this->getUrl('*/*/massDelete'),
                'confirm' => array(
                    'title' => Mage::helper('adminhtml')->__('Delete Items'),
                    'message' => Mage::helper('adminhtml')->__('Are you sure you want to delete these items?')
                )
            ));
        }
        return parent::_addMassaction();
    }
    }
	

Step 4: Register the grid in etc/adminhtml/routes.xml file

Create a new directory app/code/local/MyCompany/MyModule/etc/adminhtml and add the following routes.xml file:

	<?xml version="1.0"?>
	<config>
		<adminhtml>
			<acl>
				<resources>
					<admin> <!-- You need to have this resource defined -->
						<children>Mymodule</children>
					</admin>
				</resources>
			</acl>
			<routers>
				<adminhtml>
					<uses> <!-- Use the default admin router -->
						<default/>
						<mymodule> <!-- Define our custom router -->
							<module>MyCompany_MyModule</module>
							<frontName>mymodule</frontName>
						</mymodule>
					</uses>
				</adminhtml>
			</routers>
		</adminhtml>
	</config>