How to use a external Script to run Magento Code.

To make any external script to perform any task we need to include ‘app/Mage.php‘ of our Magento installation. Then, we can use the code of magento in that external script.
For example, to fetch Product data from Magento shop in any external script.

/**
 * Include Mage.php of your Magento installation
 */
require_once("../magento/app/Mage.php");

Mage::app('default'); 
/**
 * To get Product Data
 * For example productId is '11'
 */
$productId = 11;
$product = Mage::getModel('catalog/product')->load($productId);  
/**
 *To Print name,,sku, price and quantity of the product
 */
echo "Name: ".$product->getName();
echo "Sku: ".$product->geSku();
echo "Price: ".$product->getPrice();
echo "Quantity: ".$product->getStockItem()->getQty();
 
/**
 * To Get all products
 */
$allProducts = Mage::getModel('catalog/product')
               ->getCollection();
 

If you have any further queries, please feel free to comment on it.