Filter module for OpenCart

Project description:
A custom filter module for OpenCart 3 — a high-performance solution for product filtering, developed from scratch without using the standard OpenCart mechanism. The main goal is to provide accurate, fast, and user-friendly product filtering based on AND-logic, similar to Hotline or Rozetka.

Key features:
• Filtering with AND-logic support — products match all selected parameters simultaneously, not just any of them
• Own table product_filter_index — pre-generated indexes for fast query processing, minimal database load
• Cascading filters — after selecting a filter, only relevant options are displayed for further refinement
• Instant product count for each option without page reload
• Full independence from standard OpenCart functionality — custom logic that is easily scalable to any needs
• SEO-optimized search

Technologies:
• PHP (OOP), MySQL, JavaScript (AJAX)
• OpenCart 3.x (without core modifications)
• SQL query optimization and index usage for maximum speed

Result:
The module significantly increased filtering speed even on large catalogs (>50,000 products), improved UX, and reduced server load compared to standard solutions. Its flexible architecture allows easy adaptation to any online store theme.