CI Paypal Library Can Not Show Multi Item_name [SOLVED]

[eluser]coma[/eluser]
Hi, I need help with CI paypal library, I have multi add to cart button and retrieve data from MySQL. My problem is i have added item name post variable for several products/items but in sandbox it only show an input field for description and unit price.I have follow the documentation for adding multiple item_name, amount and quantity, here's my sample code:

Code:

$this->paypal_lib->add_field('item_name_1','abc');
$this->paypal_lib->add_field('item_number_1','1');
$this->paypal_lib->add_field('amount_1', '50');
$this->paypal_lib->add_field('quantity_1', '5');
            
            
$this->paypal_lib->add_field('item_name_2','abcd');
$this->paypal_lib->add_field('item_number_2','2');
$this->paypal_lib->add_field('amount_2', '50');
$this->paypal_lib->add_field('quantity_2', '5');

Please give me a favor about my problem above.Thank you

Regards,