kanampalli

$product = Mage::getModel('catalog/product')->load(87);  // Random product ID

// get cart and add product
$cart = Mage::getSingleton('checkout/cart'); 
$cart->init();
$cart->addProduct($product, 2);

// update session
$session->setCartWasUpdated(true);

kanampalli

/* Details of products and stores: */
<?php
/**
 * @author      MagePsycho <info@magepsycho.com>
 * @website     http://www.magepsycho.com
 * @category    using Header / Footer outside of Magento
 */
$mageFilename = '/var/www/html/magento1.9/app/Mage.php';
require_once $mageFilename;