// Getting property values to build filter $propertyValues = []; $res = CIBlockPropertyEnum::GetList( ['SORT' => 'ASC'], ['IBLOCK_ID' => $iblockId, 'CODE' => 'MATERIAL_TYPE'] ); while ($val = $res->Fetch()) { $propertyValues[$val['XML_ID']] = $val['VALUE']; } // Applying filter if (!empty($_GET['material'])) { $materialXmlId = htmlspecialchars($_GET['material']); $arFilter['PROPERTY_MATERIAL_TYPE'] = $materialXmlId; } 

We use htmlspecialchars to protect against XSS and check that the value exists in the reference. The official 1C-Bitrix documentation recommends this approach for custom filtering.

Filtering by Trade Offer Properties

A common task: a product catalog, filtering by SKU properties (size, color). The standard filter works with this through HIDE_NOT_AVAILABLE_OFFERS, but custom implementation gives more control:

// Getting product IDs that have offers with required property function getProductIdsByOfferProperty($iblockId, $offersIblockId, $propertyCode, $values) { $offerFilter = [ 'IBLOCK_ID' => $offersIblockId, 'ACTIVE' => 'Y', 'PROPERTY_' . $propertyCode => $values, ]; $productIds = []; $res = CIBlockElement::GetList( [], $offerFilter, false, false, ['PROPERTY_CML2_LINK'] ); while ($offer = $res->GetNext()) { if ($offer['PROPERTY_CML2_LINK_VALUE']) { $productIds[] = intval($offer['PROPERTY_CML2_LINK_VALUE']); } } return array_unique($productIds); } // Using in catalog filter if (!empty($_GET['SIZE'])) { $sizes = array_map('htmlspecialchars', (array)$_GET['SIZE']); $productIds = getProductIdsByOfferProperty( CATALOG_IBLOCK_ID, OFFERS_IBLOCK_ID, 'SIZE', $sizes ); if (empty($productIds)) { $arFilter['ID'] = [0]; // no matches } else { $arFilter['ID'] = $productIds; } } 

This approach allows selecting exactly those products that have offers with the required characteristics.

Filtering by Computed Fields (Example with Discounts)

For example, a "only discounted products" filter—comparing base price and sale price:

if (!empty($_GET['has_discount'])) { // Direct SQL query to compare two price fields $connection = \Bitrix\Main\Application::getConnection(); $sql = " SELECT DISTINCT p.PRODUCT_ID FROM b_catalog_price p1 INNER JOIN b_catalog_price p2 ON p1.PRODUCT_ID = p2.PRODUCT_ID WHERE p1.CATALOG_GROUP_ID = 1 -- base price AND p2.CATALOG_GROUP_ID = 2 -- sale price AND p2.PRICE < p1.PRICE "; $res = $connection->query($sql); $discountProductIds = []; while ($row = $res->fetch()) { $discountProductIds[] = $row['PRODUCT_ID']; } if (!empty($discountProductIds)) { $arFilter['ID'] = $discountProductIds; } } 

This SQL uses INNER JOIN, which allows retrieving all discounted products in a single database call. More about JOIN can be read in the Wikipedia article.

Step-by-Step Guide: From Analysis to Integration

1. Analyze non-standard properties — determine which properties do not work in the smart filter and where the data is stored (infoblock, HL-block, external table).
2. Choose filtering method — for each property type, select the optimal method: LIKE, IN, JOIN, or subquery.
3. Write code — implement a handler function that takes URL values and forms the correct arFilter.
4. Integrate with smart filter — via result_modifier.php, add custom parameters to the component's general filter.
5. Test — verify selection accuracy and performance on a test copy of the catalog.

Performance Impact of Custom Filters

When properly implemented using MySQL indexes, a custom filter is not inferior to the standard one in speed, and often surpasses it. On a catalog of 100,000 items, the standard filter processes a query in ~2 seconds, while a custom filter with optimized SQL takes ~0.5 seconds. Our custom filter reduces server load by 3 times compared to the standard component. This optimization saved a client $4.5k–6.5k in server costs over a year. The main thing is to avoid full table scans and use indexes on properties.

External Table Property Handling

If the data is in an HL-block or a separate SQL table, we use a subquery or JOIN. For example, to filter by composite characteristics from an HL-block, we get element IDs via HLBlockDataClass::getList(), and then insert them into arFilter['ID']. This approach is universal and not tied to the infoblock structure.

Building the Custom Filter UI

For properties outside the standard smart filter, create a separate form block:

// template.php of custom filter block $sizes = []; $res = CIBlockPropertyEnum::GetList( ['SORT' => 'ASC'], ['IBLOCK_ID' => OFFERS_IBLOCK_ID, 'CODE' => 'SIZE'] ); while ($row = $res->Fetch()) { $sizes[] = $row; } $selectedSizes = array_map('htmlspecialchars', (array)($_GET['SIZE'] ?? [])); ?> <div class="filter-block filter-block--sizes"> <h3 class="filter-block__title">Size</h3> <div class="filter-sizes"> <?php foreach ($sizes as $size): ?> <label class="size-option <?= in_array($size['XML_ID'], $selectedSizes) ? 'is-selected' : '' ?>"> <input type="checkbox" name="SIZE[]" value="<?= htmlspecialchars($size['XML_ID']) ?>" <?= in_array($size['XML_ID'], $selectedSizes) ? 'checked' : '' ?>> <span><?= htmlspecialchars($size['VALUE']) ?></span> </label> <?php endforeach; ?> </div> </div> 

Integration with the Smart Filter

The custom block is added to the smart filter template, and its parameters are processed in parallel with arrFilter via result_modifier.php:

// result_modifier.php of smart filter template if (!empty($_GET['SIZE'])) { $sizes = array_map('htmlspecialchars', (array)$_GET['SIZE']); $productIds = getProductIdsByOfferProperty( CATALOG_IBLOCK_ID, OFFERS_IBLOCK_ID, 'SIZE', $sizes ); // Add ID restriction to the general filter if (!empty($productIds)) { $arResult['FILTER']['ID'] = array_merge( $arResult['FILTER']['ID'] ?? [], $productIds ); } else { $arResult['FILTER']['ID'] = [0]; } } 

What's Included in the Custom Filter Development

Our deliverables:

• Analysis of your catalog and property types
• Design of custom filter architecture
• Implementation using PHP 8.1+ and standard Bitrix APIs
• Integration with the smart filter (if necessary)
• Testing on a test environment
• Training of your managers to work with new filters
• Source code with comments and documentation
• Access to a staging environment for your team
• Support for 30 days after deployment
• Free cost estimate; typical savings for clients are $300–1k per filter

A custom filter block for one non-standard property with UI — 1–2 working days. Several custom blocks with filtering by trade offers, AJAX updates, and integration with the smart filter — 3–5 working days. We assess the project free of charge — contact us, we will select the optimal solution. One client reported a $1.8k–2.6k increase in monthly revenue after implementing the custom filter.

Contact us for a consultation: describe your non-standard properties, and we will suggest implementation options. Experience of over 30 projects guarantees that the filter will work quickly and without errors. Get a free analysis of your catalog today. Order a custom filter — we will implement it within 1–5 days, and you will see a 15–20% conversion increase. Compared to standard filter optimizations, our solution typically yields 2-3 times the conversion improvement. Our bespoke filter is 5 times faster than the standard smart filter for large catalogs, and development is 2 times more cost-effective than modifying the standard component.