<?php
require_once($_SERVER['DOCUMENT_ROOT'] . "/bitrix/modules/main/include/prolog_before.php");
?>
<?
$arEventFields= array(
    "FORM_DROPDOW_THEME" => $_POST['form_dropdown_theme'],
    "NAMETEXTBOX" => $_POST["NameTextbox"],
    "EMAILTEXTBOX" => $_POST["EmailTextbox"],
    "TELEPHONETEXTBOX" => $_POST["TelephoneTextbox"],
    "DESCRIPTIONTEXTAREA" => $_POST["DescriptionTextArea"]
);

CEvent::Send("CONTACT_US_FORM", 's1', $arEventFields, "N", 78);

unset($_POST["form_dropdown_theme"]);
unset($_POST["NameTextbox"]);
unset($_POST["EmailTextbox"]);
unset($_POST["TelephoneTextbox"]);
unset($_POST["DescriptionTextArea"]);
?>