bnfs_webhook.php

<?php
add_action('supstr-process-signup', 'bnfs_webhook_process_signup', 10, 1);

function bnfs_webhook_process_signup($atts) {
  $webhook_url = 'https://zapier.com/hooks/catch/1170913/2pv4l9/';
  $args = array(
    'method' => 'POST',
    'timeout' => 30,
    'redirection' => 5,
    'httpversion' => '1.1',
    'blocking' => true,
    'headers' => array(),
    'body' => json_encode($atts),
    'cookies' => array(),
    'sslverify' => true,
  );
  $res = wp_remote_post($webhook_url, $args);
}