whmcsTools/check_prorata.php

<?php

/**
* Detect if current cart product uses Pro Rata Option
* @author brian!
*/

use Illuminate\Database\Capsule\Manager as Capsule;

function cart_prorata_hook($vars)
{
   if ($vars['templatefile']=='configureproduct'){

       $pid = $vars['productinfo']['pid'];
       $prorata = Capsule::table('tblproducts')
               ->where('id',$pid)
               ->value('proratabilling');

       if ($prorata == "1") {
           return array("prorata" => $prorata);
       }
   }
}
add_hook("ClientAreaPageCart", 1, "cart_prorata_hook");