title: whmcs: run function when an invoice for a new order is paid
body: <p>I'm new to whmcs, and I'm developing my first &quot;Provisioning Modules&quot; if you have any good resources kindly post the link.</p>
  <p>What I want: run a function when the user pays for the module (that is a service). Why? to run specific API for that services.</p>
  <p>I found those functions: <a href="https://developers.whmcs.com/provisioning-modules/supported-functions/" rel="nofollow noreferrer">https://developers.whmcs.com/provisioning-modules/supported-functions/</a></p>