Core Concepts

Core Concepts

A primer on how HOF thinks. Read this once and the rest of the docs make 10x more sense.

what's a facet?

A facet is a single filter dimension. "Price." "Color." "Category." "On sale." It's one axis along which a user can narrow a list.

A facet set is a group of facets that work together on a results page. The classic example: a shop sidebar with Price + Color + Size + In Stock.

indexed vs. live queries

Most cheap filter plugins build their queries on the fly. Every time a user moves a slider, the plugin runs a fresh WP_Query with tax_query and meta_query joins. This is fine for 50 products. It implodes at 5,000.

HOF maintains a custom index table that flattens facet data into a fast lookup structure. Filter clicks hit the index, not your products table. You can have 100,000 products and filters still feel instant.

the data flow

flowchart LR
    A[Product / Post created or updated] --> B[Indexer hook fires]
    B --> C[(HOF index tables)]
    D[Visitor clicks facet] --> E[Frontend signal updates]
    E --> F[REST request to HOF endpoint]
    F --> C
    C --> G[Filtered IDs returned]
    G --> H[Listing re-renders]

Loading

The indexer is event-driven — it updates when a product changes, not on a cron. (A scheduled full re-index is available for cases where the event hook misses something.)

facet types

HOF ships 16 facet types. A representative handful:

Type	Use case
Checkbox	Multi-select categories, tags, attributes
Radio	Single-select (rare but useful)
Dropdown	Long lists where space matters
Range Slider	Price, weight, numeric meta
Date Range	Events, posts by published date
Search	Free-text within the result set
Hierarchy	Nested taxonomies (category > sub-category)
Color Swatch	Variation colors, attribute swatches
Toggle	Boolean filters ("In stock", "On sale")

→ Full Facet Types catalog with all 16 types, a decision tree, and the shared config schema.

state lives in the URL

Every facet selection updates the URL. That means:

• Shareable filtered views. Send a link, get the same filter state.
• Browser back/forward works. Like the web should.
• SEO-friendly. Crawlers see real URLs, not fragments.

next reads

• 🏗️ Architecture — the technical stack
• 👨‍💻 Developer Guide — hooks, APIs, extending