Setting up a price reduction notification for 1C-Bitrix products

Configuration of Price Drop Notification in 1C-Bitrix

Product price drops — need to notify users who added it to favorites or explicitly subscribed to price drops. The mechanism consists of two parts: tracking price changes and sending notifications to interested users. In Bitrix, both components are implemented without third-party services.

Capturing price changes

Catalog prices are stored in b_catalog_price. When price changes via API (CCatalogProduct::SetPrice() or \Bitrix\Catalog\PriceTable::update()), the OnCatalogPriceUpdate event fires. Subscribe to it:

AddEventHandler('catalog', 'OnCatalogPriceUpdate', function($fields) {
    $productId = $fields['PRODUCT_ID'];
    $newPrice   = $fields['PRICE'];
    $typeId     = $fields['CATALOG_GROUP_ID']; // price type

    // Get old price from our snapshot table
    $oldPrice = PriceSnapshotTable::getLastPrice($productId, $typeId);

    if ($oldPrice && $newPrice < $oldPrice) {
        // Queue notification task
        PriceDropQueue::add($productId, $newPrice, $oldPrice);
    }

    // Save new snapshot
    PriceSnapshotTable::save($productId, $typeId, $newPrice);
});

Snapshot table bl_price_snapshot: fields product_id, catalog_group_id, price, currency, recorded_at.

Storing user subscriptions

Create bl_price_watch table with fields:

• user_id — ID from b_user (NULL for anonymous)
• email — notification email
• product_id — product ID
• target_price — desired price (optional, NULL = any drop)
• created_at
• notified_at — date of last notification

"Watch price" button on product page sends AJAX request, which inserts row in bl_price_watch. For authorized users, email is taken automatically from b_user.

Sending notifications

Agent runs every 30 minutes. Reads bl_price_drop_queue and for each product finds subscribers in bl_price_watch where target_price IS NULL OR target_price >= new_price. Notification is sent via \Bitrix\Main\Mail\Event::send() with type CATALOG_PRICE_DROP:

\Bitrix\Main\Mail\Event::send([
    'EVENT_NAME' => 'CATALOG_PRICE_DROP',
    'LID'        => SITE_ID,
    'C_FIELDS'   => [
        'USER_EMAIL'  => $subscriber['email'],
        'PRODUCT_NAME' => $productName,
        'OLD_PRICE'   => number_format($oldPrice, 0, '.', ' '),
        'NEW_PRICE'   => number_format($newPrice, 0, '.', ' '),
        'PRODUCT_URL' => $productUrl,
        'DISCOUNT_PCT' => round((1 - $newPrice / $oldPrice) * 100),
    ],
]);

After sending, set notified_at = NOW() and can add logic: don't notify again on same product more than once per 7 days.

What to configure

• OnCatalogPriceUpdate handler with snapshot table write and queue recording
• bl_price_snapshot and bl_price_watch tables
• "Watch price" button UI in catalog.element component template
• CATALOG_PRICE_DROP mail event type and HTML letter template
• Notification agent with deduplication by notified_at