KoolTabs allows you to define unlimited level of tabs easily with addTab() function.
You may have a look at our source-code for more details.
<?php
require $KoolControlsFolder."/KoolTabs/kooltabs.php";
$kts = new KoolTabs("kts");
$kts->styleFolder = "silver";
$kts->addTab("root","home","Home",null,true);
$kts->addTab("root","products","Products");
$kts->addTab("root","services","Services");
$kts->addTab("root","company","Company");
$kts->addTab("root","contactus","Contact us");
$kts->addTab("home","intro","Introduction",null,true);
$kts->addTab("home","strategy","Strategy",null,true);
$kts->addTab("products","kooltreeview","KoolTreeView");
$kts->addTab("products","koolslidemenu","KoolSlideMenu");
$kts->addTab("services","oursource","Out-sourcing");
$kts->addTab("services","consultant","Consultant Services");
$kts->addTab("company","aboutus","About us");
$kts->addTab("company","keystaffs","Key staffs");
$kts->addTab("contactus","headquater","Head Quater");
$kts->addTab("contactus","branches","Branches");
?>
<form id="form1" method="post">
<div style="padding:10px;">
<?php echo $kts->Render();?>
</div>
</form>