//Function to create a new user after a successful Paypal payment
function DK_gf_add_user( $entry, $feed, $transaction_id, $amount ) {

  if( rgar( $entry, 'form_id' ) == '2') {
    // get first and last name from $entry
    $order_id = rgar( $entry, 'id' );
    $email_address = rgar( $entry, '2.14' );
    $first_name = rgar( $entry, '2.1.3' );
    $last_name = rgar( $entry, '2.1.6' );

    $m_first_name = rgar( $entry, '2.2.3' );
    $m_last_name = rgar( $entry, '2.2.6' );

    if( null == username_exists( $email_address ) ) {

      // Generate the password and create the user
      $password = wp_generate_password( 12, false );
      $user_id = wp_create_user( $email_address, $password, $email_address );

      // Set the wordpress values
      wp_update_user(
        array(
          'ID'          =>    $user_id,
          'nickname'    =>    $email_address,
          'first_name'  =>    $first_name,
          'last_name'   =>    $last_name,
        )
      );

      // Set acf values
      update_field('field_5a98e59f5b8f3', $user_id, 'user_'.$user_id);
      update_field('field_5a98e211d1623', $m_first_name, 'user_'.$user_id);
      update_field('field_5a98e1f5d1622', $m_last_name, 'user_'.$user_id);


      // Set the role
      $user = new WP_User( $user_id );
      $user->set_role( 'contributor' );

      // Email the user
      wp_mail( $email_address, 'Welcome!', 'Your Password: ' . $password );

    } else {
      //code if user already registered
    } // end if
  }

}
add_action( 'gform_paypal_fulfillment', 'DK_gf_add_user', 10, 4 );