Magento从外部文件添加到购物车不起作用

i have a problem with Magento's addProduct() function. I have the following code:

<?php
// Mage init
include_once '../app/Mage.php'; 
umask(0);  
Mage::init('default');
Mage::getSingleton('core/session', array('name' => 'frontend'));
// Get customer session
$session = Mage::getSingleton('customer/session');     
// Get cart instance
$cart = Mage::getSingleton('checkout/cart'); 
$cart->init();    
// Add a product with custom options
$productId = 11348;
$productInstance = Mage::getModel('catalog/product')->load($productId);
$param = array(
    'product' => $productInstance->getId(),
    'qty' => 1,
    'options' => array(
        528 => '1756',   // Custom option with id: 528
        527 => '1753',   // Custom option with id: 527
        526 => '1751'   // Custom option with id: 526
    )
);
$request = new Varien_Object();
$request->setData($param);
$cart->addProduct($productInstance, $request);    
// update session
$session->setCartWasUpdated(true);    
// save the cart
$cart->save();     
?>

It worked yesterday so include and $param are rigth but now it doesn't work. You also can add this product to cart inside the shop so the product exist and it's in stock. This code doesn't seems to have any error but it doesn't add product to cart.

Thanks for help.

try with adding form key and uenc field

$param = array(
'product' => $productInstance->getId(),
'form_key'=>$form_key_put_here,
'uenc' =>Mage::app()->getRequest()->getParam('uenc', 1),
'qty' => 1,
'options' => array(
    528 => '1756',   // Custom option with id: 528
    527 => '1753',   // Custom option with id: 527
    526 => '1751'   // Custom option with id: 526
));

hope this will help.

<?php
require_once('app/Mage.php');    
umask(0);
Mage::app('admin');
$product_model = Mage::getModel('catalog/product');
$my_product_sku = 'test';        
$my_product_id  = $product_model->getIdBySku($my_product_sku);
$my_product     = $product_model->load($my_product_id);
$qty_value = 13;
$cart = Mage::getModel('checkout/cart');
$cart->init();
$cart->addProduct($my_product, array('qty' => $qty_value));
$cart->save();

Mage::getSingleton('checkout/session')->setCartWasUpdated(true); 
?>