Sub-Title

Block Overview

Property	Value
Name	core/heading (variation: sub-title)
Title	Sub-title
Category	Core heading variation
Description	Displays and edits the post sub-title via block bindings to sub_title post meta.

The legacy prc-block/subtitle block remains registered in the deprecated folder for backward compatibility with existing content, but it is no longer insertable.

Registration and assets

• Client (block-bindings.js): registers a core/heading variation named sub-title with metadata.bindings.content pointing at core/post-meta (key: sub_title) and className: is-style-sub-title.
• Styles (style.scss): the is-style-sub-title block style applies serif italic typography, fluid font sizing, and sub-title spacing on the frontend and in the editor.
• Server (class-core-heading.php):
  • Registers sub_title and legacy sub_headline post meta with show_in_rest: true.
  • Strips duplicate bound sub-title headings rendered inside core/post-content.
  • Suppresses empty bound sub-title headings on the frontend.
• Legacy block (deprecated/src/sub-title/): prc-block/subtitle remains registered with "inserter": false. Its render callback returns empty output on the frontend; the editor UI remains available for unmigrated in-content instances.

Data flow and post meta

Layer	Meta key(s)	Behavior
Editor	sub_title	Edited directly in the canvas through core's post-meta block binding on the core/heading sub-title variation.
Frontend (PHP)	sub_title	Core's binding processor fills the heading content from post meta. Core_Heading::render_sub_title_heading() suppresses empty output.
Legacy editor	sub_title	Unmigrated prc-block/subtitle instances still read/write sub_title via useEntityProp.

Usage Instructions

1. Insert the Sub-title variation from the heading block inserter.
2. Type the sub-title in the canvas. Core binds the heading content to sub_title post meta.
3. Use heading block controls for alignment and other overrides. Typography and spacing come from the Sub-title block style (is-style-sub-title).
4. Place a bound sub-title heading in post content for editing and in the theme template for display.
5. Duplicate in-content sub-titles are stripped on the frontend when the template already renders one.

Block Markup Example

<!-- wp:heading {"level":2,"className":"is-style-sub-title","metadata":{"bindings":{"content":{"source":"core/post-meta","args":{"key":"sub_title"}}}}} -->
<h2 class="wp-block-heading is-style-sub-title">
	This is the sub-title text for the article
</h2>
<!-- /wp:heading -->

Migration

Two WP-CLI commands are available under wp prc block-library:

Command	Purpose
migrate-sub-headline	Copies legacy sub_headline meta to sub_title.
migrate-subtitle-block	Converts in-content prc-block/subtitle blocks to bound core/heading.

Both default to dry-run mode. Pass --dry-run=false to write changes.

Related Blocks

• core/post-title — The main post title block. Sub-title is typically placed immediately after it.
• core/post-content — In-content bound sub-title headings are stripped when they would duplicate the template display.