Adds in Paypal Standard Payment gateway support for EVP Wallet System addon.

Provides access to Paypal IPN Debug and Paypal Sandbox for debugging purposes.

Paypal IPN Debug: Enabling will write PayPal IPN response in ipn.log file at /public_html/tmp/logs/ folder. Make sure to remove any log data from logs folder in a production server. As it may contain sensitive information.

Paypal Sandbox: This allows a developer to test a payment processing checkout using a sandbox paypal account without making any real purchase. More info.

To configure Paypal standard payment properly, adjust these settings in your Paypal account:

1. Visit website payment preference https://paypal.com/businessmanage/preferences/website 

Enable both options as image. https://d.pr/i/KYWWNL

Auto return -> ON: https://yourdomain.com/members/success.php

Payment Data Transfer-> ON

2. Set IPN as explained before like this image : https://d.pr/i/vEC0as

Make sure Message Delivery is active. IPN URL is not recommended to be correct as proper IPN URL gets sent through a form submission by default through EVP Paypal Addons which overrides it. But if required. Then set direct IPN URL: https://yourdomain.com/lib/addons/paypal-standard-payment-gateway/ipn.php

3. Disable Review each payment before completing/confirming [If Enable]