add-navbar-link.php

<?php

/**
 * Add an item to the primary WHMCS navigation bar when the logged in client is
 * an affiliate.
 *
 * @see http://docs.whmcs.com/Editing_Client_Area_Menus
 * @see http://docs.whmcs.com/Using_Models
 * @see http://docs.whmcs.com/classes/classes/WHMCS.User.Client.html
 */

use WHMCS\View\Menu\Item as MenuItem;

add_hook('ClientAreaPrimaryNavbar', 1, function (MenuItem $primaryNavbar) {
    /** @var \WHMCS\User\Client $client */
    $client = Menu::context('client');

    if (!is_null($client) && $client->affiliate()->exists()) {
        $primaryNavbar->addChild('Menu Name')
            ->setUri('https://www.example.com/')
            ->setOrder(70);
    }
});