Error in Paypal Module - payment not processed - variable "str" undefined

[kateclouds]

Dear All, 

I am using Prestashop 1.6.1.11, and the native PayPal module 3.11.4 doesn't work. I've asked to the PayPal technical staff, they told me that there is a problem within the variable "str". None of the "if" is called, so that the "token" isn't populated. 

Here follows the code. 

Can you suggest how to fix the problem? 

Did you find similar issues? 

Thank you 

Caterina 

 

 

var str = '';

  if($('.paypal_payment_form input[name=id_product]').length > 0)

str = '&id_product='$('.paypal_payment_form input[name=id_product]').val();

  if($('.paypal_payment_form input[name=quantity]').length > 0)

str = '&quantity='$('.paypal_payment_form input[name=quantity]').val();

  if($('.paypal_payment_form input[name=id_p_attr]').length > 0)

str = '&id_p_attr='$('.paypal_payment_form input[name=id_p_attr]').val();