Magento: Override Mage_Adminhtml_Block_Report_Product_Lowstock_Grid

1. Create a file in app\etc\modules\Techievolve_LowStockReport.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
      <Techievolve_LowStockReport>
         <active>true</active>
         <codePool>local</codePool>
      </Techievolve_LowStockReport>
    </modules>
</config>

2. Create a file in app\code\local\Techievolve\LowStockReport\etc\config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Techievolve_LowStockReport>
            <version>1.0.0</version>
        </Techievolve_LowStockReport>
    </modules>
    <global>
        <blocks>
            <adminhtml>
                <rewrite>
                    <report_product_lowstock_grid>Techievolve_LowStockReport_Block_Adminhtml_Report_Product_Lowstock_Grid</report_product_lowstock_grid>
                </rewrite>
            </adminhtml>
        </blocks>
    </global>
</config>

3. Create a file in app\code\local\Techievolve\LowStockReport\Block\Adminhtml\Report\Product\Lowstock\Grid.php

<?php

/**
 * Adminhtml low stock products report grid block override
 *
 * @category    Report Collection
 * @author      Sushant
 */

class Techievolve_LowStockReport_Block_Adminhtml_Report_Product_Lowstock_Grid extends Mage_Adminhtml_Block_Report_Product_Lowstock_Grid {
    
    protected function _prepareCollection() {
        if ($this->getRequest()->getParam('website')) {
            $storeIds = Mage::app()->getWebsite($this->getRequest()->getParam('website'))->getStoreIds();
            $storeId = array_pop($storeIds);
        } else if ($this->getRequest()->getParam('group')) {
            $storeIds = Mage::app()->getGroup($this->getRequest()->getParam('group'))->getStoreIds();
            $storeId = array_pop($storeIds);
        } else if ($this->getRequest()->getParam('store')) {
            $storeId = (int)$this->getRequest()->getParam('store');
        } else {
            $storeId = '';
        }

        /** @var $collection Mage_Reports_Model_Resource_Product_Lowstock_Collection  */
        $collection = Mage::getResourceModel('reports/product_lowstock_collection')
            ->addAttributeToSelect('*')
            ->addAttributeToFilter('status', '1')
            ->setStoreId($storeId)
            ->filterByIsQtyProductTypes()
            ->joinInventoryItem('qty')
            ->useManageStockFilter($storeId)
            ->useNotifyStockQtyFilter($storeId)
            ->setOrder('qty', Varien_Data_Collection::SORT_ORDER_ASC);
        if( $storeId ) {
            
            $collection->addStoreFilter($storeId);
        }
        //echo "<pre>"; print_r($collection->getData()); exit;
        $this->setCollection($collection);
        //return parent::_prepareCollection();
        return Mage_Adminhtml_Block_Widget_Grid::_prepareColumns();
    }
}