PayPal with IPN enabled causing error on cmd = "_cart"

Question

I am using PayPal Website Payment Standard with IPN enabled.

Before I set cmd variable like this

<input type="hidden" name="cmd" value="_xclick">

but then I tied it to

<input type="hidden" name="cmd" value="_cart">

I also changed some other variables inside my form

<input type="hidden" name="item_name_1" value="Item1">
<input type="hidden" name="amount_1" value="2">
<input type="hidden" name="item_name_2" value="Item2">
<input type="hidden" name="amount_2" value="2">
<input type="hidden" name="quantity_1" value="1">
<input type="hidden" name="quantity_2" value="2">
<input type="hidden" name="item_number_1" value="121">
<input type="hidden" name="item_number_2" value="122">

But when the form is submitted to PayPal, I get this error.

Thanks at Advance ...

Answer 1

Have you added a target="paypal"form opening tag?

Could you show the whole form?

Answer 2

I think you need to include the upload variable to identify the form as a basket:

<input type="hidden" name="upload" value="1">