Magento 1.8+/1.9+ 无法更新购物车产品数量 Quantity in checkout shopping cart doesn't work pr...

In your theme directory

In your /app/design/frontend/yourthemepackage/default/template/checkout/cart.phtml file OR /app/design/frontend/default/yourtheme/template/checkout/cart.phtml file

<form action="<?php echo $this->getUrl('checkout/cart/updatePost') ?>" method="post">
<?php echo $this->getBlockHtml('formkey'); ?>  <!-- this line must be there -->