README

A drop-in Contao bundle that fixes Isotope's Cumulative Filter module to use deterministic, content-based URL parameters — preventing search engine robots from crawling an infinite stream of unique filter URLs. No reconfiguration required.

The Problem

Isotope's native Cumulative Filter stores each unique filter combination as a row in tl_iso_requestcache and exposes the row's auto-increment integer ID in the URL as ?isorc=<id>. Because every unique filter combination produces a new, never-before-seen integer ID, search engine robots encounter an endless supply of distinct URLs and can crawl indefinitely — consuming crawl budget and potentially causing indexing issues.

The Solution

This bundle replaces the auto-increment integer in ?isorc= with a deterministic MD5 hash of the filter configuration. The same combination of filters always produces the same hash, so robots never encounter a URL they haven't already seen. Pages with active filter parameters are also marked noindex,nofollow automatically.

The hash is resolved back to the corresponding database row ID transparently before Isotope's native lookup runs, so Isotope core requires no modifications and your existing frontend modules require no reconfiguration.

Requirements

• PHP ^7.4 || ^8.0
• Contao ^4.13 || ^5.3
• Isotope eCommerce (with the iso_cumulativefilter frontend module)

Installation

composer require bright-cloud-studio/contao-isotope-cumulative-filter

After installation, run a Contao database update if prompted. Your existing Cumulative Filter modules will immediately use the new behaviour — no changes in the backend are needed.

How It Works

Module Override

The bundle registers its extended class against Isotope's existing iso_cumulativefilter key in $GLOBALS['FE_MOD'], replacing the default class transparently. Your existing Cumulative Filter frontend modules continue to work as-is — they just now go through the extended class instead of Isotope's original.

The extended class intercepts the filter save request, persists the filter state via Isotope's own RequestCache::saveNewConfiguration(), then reads the config_hash column and redirects to ?isorc=<hash> instead of ?isorc=<id>.

InitializeRequestCacheListener (Hook: initializeSystem)

Fires before Isotope initialises. When ?isorc= contains a 32-character hex hash, it looks up the corresponding integer ID in tl_iso_requestcache and rewrites $_GET['isorc'] in place. Isotope's unmodified RequestCache::findByIdAndStore() then proceeds normally. If the hash is not found (cache purged or stale URL), the parameter is removed entirely so Isotope does not mark the page as invalid.

GeneratePageListener (Hook: generatePage)

Detects requests containing isorc or cumulativefilter query parameters and sets the page's robots directive to noindex,nofollow, keeping filtered pages out of search engine indexes.

License

LGPL-3.0-or-later. See LICENSE for full terms.

Credits

Developed by Mark St. Jean at Bright Cloud Studio.