title: Meaning of Auth in PayPal(Standard) Subscribe Button Return URL?
body: <p>I have a subscribe button (using PayPal Payments Standard Integration) in my WordPress website.</p>
  
  <pre><code>&lt;form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post"&gt;
  &lt;input type="hidden" name="cmd" value="_xclick-subscriptions"&gt;
  &lt;input type="hidden" name="business" value="FRG9AB9A93MUN"&gt;
  &lt;input type="hidden" name="lc" value="US"&gt;
  &lt;input type="hidden" name="item_name" value="Premium Subscription"&gt;
  &lt;input type="hidden" name="item_number" value="321"&gt;
  &lt;input type="hidden" name="no_note" value="1"&gt;
  &lt;input type="hidden" name="no_shipping" value="1"&gt;
  &lt;input type="hidden" name="rm" value="1"&gt;
  &lt;input type="hidden" name="return" value="http://example.com/success"&gt;
  &lt;input type="hidden" name="cancel_return" value="http://example.com/cancel"&gt;
  &lt;input type="hidden" name="src" value="1"&gt;
  &lt;input type="hidden" name="a3" value="299.00"&gt;
  &lt;input type="hidden" name="p3" value="1"&gt;
  &lt;input type="hidden" name="t3" value="M"&gt;
  &lt;input type="hidden" name="currency_code" value="USD"&gt;
  &lt;input type="hidden" name="bn" value="PP-SubscriptionsBF:btn_subscribeCC_LG.gif:NonHosted"&gt;
  &lt;input type="image" src="https://www.sandbox.paypal.com/en_US/i/btn/btn_subscribeCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!"&gt;
  &lt;img alt="" border="0" src="https://www.sandbox.paypal.com/en_US/i/scr/pixel.gif" width="1" height="1"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>I am testing the functionality using PayPal Sandbox. I use WordPress PayPal Framework Plugin (<a href="http://wordpress.org/extend/plugins/paypal-framework" rel="nofollow noreferrer">http://wordpress.org/extend/plugins/paypal-framework</a>)</p>
  
  <h2>My Question</h2>
  
  <p>Upon successful payment(subscription), buyer returns to the return url with 'auth' and 'form_charset'
  (<a href="http://example.com/success/?auth=AtKlH609fYvJhW2wmFr9iMmXboz9JEB64TJjNpLVH8d0OlBbnOpn-TeeCvZT6VWOcoo8XG4GD0AeftCUMdNWCAQ&amp;form_charset=UTF-8" rel="nofollow noreferrer">http://example.com/success/?auth=AtKlH609fYvJhW2wmFr9iMmXboz9JEB64TJjNpLVH8d0OlBbnOpn-TeeCvZT6VWOcoo8XG4GD0AeftCUMdNWCAQ&amp;form_charset=UTF-8</a>)</p>
  
  <blockquote>
    <p>Can someone explain me the meaning of 'auth' and 'form_charset'? Can I
    use it to obtain further information about the transaction via NVP
    API? Then what should be the NVP API method I should use?</p>
  </blockquote>
  
  <p>I can properly receive IPN messages on these transactions.</p>
  
  <h2>What I have done so far</h2>
  
  <p>I am conversant on PayPal Express Checkout Integration, capturing IPN msgs and processing them, etc.</p>
  
  <p>I have read the NVP API methods, requests and responses in the PayPal Guide.
  <a href="https://cms.paypal.com/cms_content/CA/en_US/files/developer/PP_NVPAPI_DeveloperGuide.pdf" rel="nofollow noreferrer">https://cms.paypal.com/cms_content/CA/en_US/files/developer/PP_NVPAPI_DeveloperGuide.pdf</a></p>
  
  <p>I went through some of the other PayPal Guides as well.</p>
  
  <p>The following question mentions about 'encrypted variable named auth'. But it was not helpful for me.
  (<a href="https://stackoverflow.com/questions/13038080/paypal-sandbox-return-url">Paypal sandbox return url</a>)</p>
  
  <p>This question also deals with return on success.
  (<a href="https://stackoverflow.com/questions/13471639/paypal-redirect-on-successful-checkout">paypal redirect on successful checkout</a>)</p>