user_ department_check.php

<?php
/**
     * check if user in department
     *
     * @param int  $iUserID
     * @param int  $iDepartmentID
     * @param bool $bCheckSubDepartments
     * @return bool
     */
    function IsInDepartment($iUserID, $iDepartmentID, $bCheckSubDepartments = true)
    {
        $arUserDepartments = CIntranetUtils::GetUserDepartments($iUserID);
        $arDepartments[]   = $iDepartmentID;
        if ($bCheckSubDepartments) {
            $arSubDepartments = CIntranetUtils::GetDeparmentsTree($iDepartmentID);
            if (!empty($arSubDepartments)) {
                foreach ($arSubDepartments as $_arDepartments) {
                    $arDepartments = array_merge($arDepartments, $_arDepartments);
                }
            }
        }
        $arDepartmentsIntersection = array_intersect($arUserDepartments, $arDepartments);
        if (!empty($arDepartmentsIntersection)) {
            return true;
        } else {
            return false;
        }
    }