<?php
require($_SERVER["DOCUMENT_ROOT"]."/bitrix/modules/main/include/prolog_before.php");

if(CModule::IncludeModule("catalog")) {

    $COUPON = CatalogGenerateCoupon();

    echo $COUPON . "<br>";

    $arCouponFields = array(
        "DISCOUNT_ID" => 3,
        "ACTIVE" => "Y",
        "ONE_TIME" => "Y",
        "COUPON" => $COUPON,
        "DATE_APPLY" => false
    );

    $CID = CCatalogDiscountCoupon::Add($arCouponFields);
    $CID = IntVal($CID);
    echo $CID . "<br>";

    echo CCatalogDiscountCoupon::CheckFields(
        "ADD", $arCouponFields
    );

    if ($CID <= 0) {
        $ex = $APPLICATION->GetException();
        $errorMessage = $ex->GetString();
        echo $errorMessage;
    }

}