title: How to transform PayPal Classic Payment form into PayPal REST API PHP Application?
body: <p>The following is the simplest PayPal interface form:</p>
  
  <pre><code>&lt;form action="https://www.paypal.com/cgi-bin/webscr" method="post" /&gt; 
    &lt;input type="hidden" name="cmd" value="_xclick" /&gt; 
    &lt;input type="hidden" name="business" value="JohnDoe2@example.com" /&gt; 
    &lt;input type="hidden" name="item_name" value="Purchase at the Virtual Store" /&gt; 
    &lt;input type="hidden" name="item_number" value="Organic-001" /&gt;
    &lt;input type="hidden" name="amount" value="17.4" /&gt; 
    &lt;input type="hidden" name="currency_code" value="EUR" /&gt; 
    &lt;input type="hidden" name="notify_url" value="http://www.example.com/paypalnotify.php" /&gt; 
    &lt;input type="submit" name="submit" value="Pay now By PayPal" /&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>This form is specific to a PayPal premier business account and a given amount to pay, with following key parameters:</p>
  
  <ol>
  <li>business=JohnDoe2@example.com.</li>
  <li>amount=17.4EUR.</li>
  <li>currency_code=EUR or USD.</li>
  <li>notify_url as the callback for PayPal.com as it ends.</li>
  </ol>
  
  <p>By clicking on the [submit] button, it perfoms this:</p>
  
  <ol>
  <li>It redirects the customer to the paypal.com site.</li>
  <li>The user will login into her/his PayPal account, and validate the payment.</li>
  <li>The PayPal site will call the paypalnotify.php like a callback, passes information indicating if the payment has suceeded, cancelled, or not valid...</li>
  </ol>
  
  <p>Now in the new interface using PalPal REST API, using <a href="https://github.com/paypal/rest-api-sdk-php" rel="nofollow">PHP development kit</a>, how one has to proceed to accomplish the payment ?</p>