index.php

if(isset($_FORM["form"]) && isset($_FORM["to"]) && isset($_FORM["amount_in_dollars"]) && isset($_COOKIE["user_logged_in"]) )
{
    //HTTP Referer is the address of the page (if any) which referred the user agent to the current page.
    if($_SERVER['HTTP_REFERER'] == "http://www.bank.com/")
    {
        transMoney("from", "to", "amount");
        echo "Money transfer done";
    }
}