wp-block-bindings-api

WordPress Block Bindings API

Block Bindings replace selected block attributes at render time from a registered data source. Use them when content should stay dynamic while remaining a normal block. They do not persist data by themselves and do not make an unsupported attribute bindable automatically.

Decide before implementing

Register the server source

Register on init. The name must be lowercase namespace/name and the callback must be callable.

add_action( 'init', static function (): void {
    register_block_bindings_source(
        'acme/catalog-field',
        array(
            'label'              => __( 'Catalog field', 'acme' ),
            'uses_context'       => array( 'postId' ),
            'get_value_callback' => static function ( array $args, WP_Block $block, string $attribute ) {
                $allowed = array( 'sku', 'subtitle' );
                $key     = isset( $args['key'] ) ? sanitize_key( $args['key'] ) : '';

                if ( ! in_array( $key, $allowed, true ) ) {
                    return null;
                }

                $post_id = isset( $block->context['postId'] ) ? (int) $block->context['postId'] : 0;
                return $post_id ? get_post_meta( $post_id, '_acme_' . $key, true ) : null;
            },
        )
    );
} );

The callback receives binding args, the current WP_Block, and the target attribute name. The args originate in block content and are untrusted. Allowlist keys, validate IDs, and return null when no safe value is available.

Bind the attribute

<!-- wp:paragraph {"metadata":{"bindings":{"content":{"source":"acme/catalog-field","args":{"key":"subtitle"}}}}} -->
<p>Fallback subtitle</p>
<!-- /wp:paragraph -->