Add To Cart Programmlly

<?php 
class Bysoft_Mycheckout_Model_Addtocart{
	
	/**
	 * When occur FATAL ERROR, it will redo the run function 
	 * @param unknown $i
	 */
	public function shutdown($i) {
		var_dump('already shutdown.');
		$last_error = error_get_last();
		var_dump($last_error);
		register_shutdown_function(array(&$this,'shutdown',$i));
		$this->run($i);
	}
	
	/**
	 * main function:
	 * 1.get the number $i `th user,
	 * 2.login it
	 * 3.get two rand product and add them to user's shopping cart, before that, clear his shopping cart
	 */
	public function run($i) {
		umask(0);
		Mage::app('admin');
		$this->i=$i;
		register_shutdown_function(array(&$this,'shutdown',$i));
		Mage::app()->setCurrentStore(1);
		$websiteId = 1;
		$arr = $this->getProductData();
		$email = 'test_' . $i . '@test.com';
		$password = 'password';
		if ($this->login_user($email,$password)) {
			$this->cleanCart();
			var_dump($this->getCartItemNum());
			if($this->getCartItemNum() < 2) {
				$product_ids = array();
				for ($j = 1; $j <= 2; ++$j) {
					$product_ids[] = $this->saveRandProduct($arr,$j);		
				}
				
				$cart = Mage::getModel('checkout/cart');
				$cart->init();
		
				$customer = Mage::getModel("customer/customer");
				$customer->setWebsiteId(1);
				$customer->loadByEmail($email);
				$customer->load($customer->getId());
				
				$quote = Mage::getSingleton('checkout/session')->getQuote();
				$quote->setCustomer($customer);
				var_dump($quote->getCustomerId());
				$cart->addProductsByIds($product_ids);
				$cart->save();
				
			}
			Mage::getSingleton('customer/session')->logout()->renewSession();
		}
	}
	
	/**
	 * get all useable product sku from a csv file.
	 * @return multitype:unknown
	 */
	public function getProductData() {
		//get product data from csv file(which products have enough stock)
		$file_path = BP . DS . 'media' . DS. 'product_inventory' . DS .'data.csv';
		$fp = fopen($file_path, 'r');
		$res = array();
		$count = 0;
		while ($data = fgetcsv($fp)) {
			if (isset($data[0]) && trim($data[0])!= '' && $count != 0) {
				$res[] = $data;
			}
			++$count;
		}
		return $res;
	}
	
	/**
	 * login a user
	 */
	public function login_user($email,$password) {
		$session = Mage::getSingleton('customer/session');
		try {
			$session->login( $email, $password );
			$session->setCustomerAsLoggedIn($session->getCustomer());
			var_dump($email . ' login successed!');
			return true;
		} catch( Exception $e ) {
			return false;
		}
	
	}
	
	/**
	 * clean current logined user's shopping cart.
	 */
	public function cleanCart() {
		if ($this->getCartItemNum() >0) {
			Mage::getSingleton('checkout/cart')->truncate()->save();
			var_dump('remove all item from cart');
		}
	}
	
	/**
	 * count current user's shopping cart item number
	 */
	public function getCartItemNum() {
		//get cart item (current login user)
		$cart = Mage::getSingleton('checkout/session');
		$cart->init();
		$quote = $cart->getQuote();
		$items = $quote->getAllVisibleItems();
		foreach ($items as $item) {
			//var_dump($item->getData());
		}
		return count($items);
	}
	
	/**
	 * get random product from a array.
	 * @param array $arr
	 * @param int $j
	 * @return int
	 */
	
	public function saveRandProduct($arr,$j) {
		while (!$_product) {
			$num = (rand(($j-1)*(floor(count($arr)/2))+1,$j*floor(count($arr)/2)));
			$product_model = Mage::getModel('catalog/product');
			$productid = $product_model->getIdBySku($arr[$num-1][0]);
			$_product = $product_model->load($productid);
		}
		return $productid;
	}	
}