Custom: Gravity Forms WP API Submission and GF API form entry creation plus send notifications

gravity-form.php

<?php
/**
 * Add WP API endpoint for form submission, then create new
 * Gravity Forms entry and send notifications.
 */

// rest api endpoint for forms submission
add_action( 'rest_api_init', function () {
  register_rest_route( 'ahr/v1', '/forms', array(
    'methods'  => 'POST',
    'callback' => __NAMESPACE__ . '\\gravity_forms_endpoint',
  ));
});

function gravity_forms_endpoint( \WP_REST_Request $request ) {
  # @TODO: sanitize inputs
  #   USE: sanitize_text_field()

  # ensure gravity forms available !!
  if (!class_exists('GFAPI')) {
    wp_send_error(array(
      'error' => true,
      'message' => 'Gravity forms plugin not enabled'
      ));
  }

  $entry_id = insertGravityFormEntry($request->get_params());

  if (is_wp_error($entry_id)) {
    wp_send_json_error( array(
      'error' => true,
      'message' => $entry_id->get_error_message(),
      'values' => $request->get_params(),
      ));
    // wp_send_json_error($resp);
  } else {
    $resp = array(
      'message' => 'Received these params',
      'entry_id' => $entry_id,
      'form' => $request->get_params(),
    );
    wp_send_json( $resp );
  }

}

/**
 * const - ID for contact-us gravity form
 */
define('GRAVITY_FORMS_CONTACT_FORM_ID', 1);

/**
 * Create new gravity forms entry for contact form, and insert it.
 *
 * Caller needs to test response with is_wp_error.
 * @thanks to https://gist.github.com/OutThisLife/bd33674bae36121a3c99
 *
 * To get a sample form entry, try: print_r( GFAPI::get_entry(<existing-form-entry-id>) );die();
 *
 * @param {array} $params - form submission params.
 * @return {mixed}  - Either the new Entry ID or a WP_Error instance
 */
function insertGravityFormEntry($params) {
  $form = \GFAPI::get_form(GRAVITY_FORMS_CONTACT_FORM_ID);
  # Build our entry

  $entry = array('form_id' => $form['id']);
  $entry['date_created'] = date('Y-m-d G:i');
  $entry[1] = $params['name'];
  $entry[2] = $params['email'];
  $entry[3] = $params['organization'];
  $entry[4] = $params['comment'];

  $entry_id_or_wperror = \GFAPI::add_entry($entry);

  if (!is_wp_error($entry_id_or_wperror)) {
    $entry = \RGFormsModel::get_lead($entry_id_or_wperror);
    \GFAPI::send_notifications($form, $entry, 'form_submission');
  }
  return $entry_id_or_wperror;
}