This library is modified by me!! (Paypal Express only). I managed to add "item list" to this library, so from single trasanction to multiple transaction is now possible.
Example code:
$params = array( 'amount' => '10', 'currency' => 'USD', 'return_url' => site_url('thankyou'), 'cancel_url' => site_url('cancelled'), 'items' => array( 'item_name' => $this->input->post('item_name'), 'item_qty' => $this->input->post('qty'), 'item_price' => $this->input->post('item_price') ) );
NOTE: each post data are arrays