Public functions for block registration, parsing, rendering, and utilities.

Block Registration

register_block_type()

Registers a block type. The recommended way is to register using block.json metadata.

register_block_type(
    string|WP_Block_Type $block_type,
    array $args = array()
): WP_Block_Type|false

Parameters:

• $block_type (string|WP_Block_Type) – Block type name including namespace (e.g., my-plugin/my-block), path to block.json, or WP_Block_Type instance
• $args (array) – Optional. Block type arguments (ignored if WP_Block_Type provided)

Returns: WP_Block_Type|false – Registered block type or false on failure

Since: 5.0.0
Since: 5.8.0 – First parameter accepts path to block.json

Example:

// Register from block.json (recommended)
register_block_type( __DIR__ . '/build' );

// Register with inline definition
register_block_type( 'my-plugin/notice', array(
    'api_version'     => 3,
    'title'           => 'Notice',
    'category'        => 'widgets',
    'render_callback' => 'render_notice_block',
    'attributes'      => array(
        'message' => array( 'type' => 'string', 'default' => '' ),
    ),
) );

---

register_block_type_from_metadata()

Registers a block type from the metadata in a block.json file.

register_block_type_from_metadata(
    string $file_or_folder,
    array $args = array()
): WP_Block_Type|false

Parameters:

• $file_or_folder (string) – Path to block.json or folder containing it
• $args (array) – Optional. Array of block type arguments to merge with metadata

Returns: WP_Block_Type|false – Registered block type or false on failure

Since: 5.5.0
Since: 5.7.0 – Added textdomain support and i18n handling
Since: 5.9.0 – Added variations and viewScript support
Since: 6.1.0 – Added render field support
Since: 6.3.0 – Added selectors field
Since: 6.4.0 – Added blockHooks support
Since: 6.5.0 – Added allowedBlocks, viewScriptModule, viewStyle support

Example:

// Register with additional render callback
register_block_type_from_metadata(
    __DIR__ . '/blocks/my-block',
    array(
        'render_callback' => 'my_block_render',
    )
);

---

unregister_block_type()

Unregisters a block type.

unregister_block_type( string|WP_Block_Type $name ): WP_Block_Type|false

Parameters:

• $name (string|WP_Block_Type) – Block type name or instance

Returns: WP_Block_Type|false – Unregistered block type or false on failure

Since: 5.0.0

Example:

// Remove the core cover block
unregister_block_type( 'core/cover' );

---

wp_register_block_metadata_collection()

Registers a block metadata collection for performance optimization.

wp_register_block_metadata_collection(
    string $path,
    string $manifest
): void

Parameters:

• $path (string) – Base path where block files reside
• $manifest (string) – Path to the manifest file

Since: 6.7.0

---

wp_register_block_types_from_metadata_collection()

Registers all block types from a metadata collection.

wp_register_block_types_from_metadata_collection(
    string $path,
    string $manifest = ''
): void

Parameters:

• $path (string) – Absolute base path for the collection
• $manifest (string) – Optional. Path to manifest file

Since: 6.8.0

---

Block Parsing

parse_blocks()

Parses blocks out of a content string.

parse_blocks( string $content ): array[]

Parameters:

• $content (string) – Post content containing blocks

Returns: (array[]) – Array of parsed block structures

Since: 5.0.0

Return Structure:

array(
    array(
        'blockName'    => 'core/paragraph',  // or null for freeform
        'attrs'        => array( 'align' => 'center' ),
        'innerBlocks'  => array( ... ),
        'innerHTML'    => '<p class="...">Content</p>',
        'innerContent' => array( 'Content', null, 'More' ),
    ),
    // ...
)

Example:

$blocks = parse_blocks( $post->post_content );
foreach ( $blocks as $block ) {
    if ( 'core/image' === $block['blockName'] ) {
        $image_id = $block['attrs']['id'] ?? null;
    }
}

---

has_blocks()

Determines whether a post or content string has blocks.

has_blocks( int|string|WP_Post|null $post = null ): bool

Parameters:

• $post (int|string|WP_Post|null) – Post content, ID, or object. Defaults to global $post

Returns: (bool) – Whether the post has blocks

Since: 5.0.0

Example:

if ( has_blocks() ) {
    // Current post uses blocks
}

if ( has_blocks( '<!-- wp:paragraph -->Test<!-- /wp:paragraph -->' ) ) {
    // String contains blocks
}

---

has_block()

Determines whether a post or string contains a specific block type.

has_block( string $block_name, int|string|WP_Post|null $post = null ): bool

Parameters:

• $block_name (string) – Full block type name (e.g., core/paragraph)
• $post (int|string|WP_Post|null) – Post content, ID, or object

Returns: (bool) – Whether the block type exists

Since: 5.0.0

Example:

if ( has_block( 'core/gallery' ) ) {
    wp_enqueue_style( 'gallery-lightbox' );
}

---

Block Rendering

render_block()

Renders a single block into HTML.

render_block( array $parsed_block ): string

Parameters:

• $parsed_block (array) – Parsed block array (from parse_blocks())

Returns: (string) – Rendered HTML

Since: 5.0.0

Example:

$block = array(
    'blockName'    => 'core/paragraph',
    'attrs'        => array( 'align' => 'center' ),
    'innerBlocks'  => array(),
    'innerHTML'    => '<p class="has-text-align-center">Hello</p>',
    'innerContent' => array( '<p class="has-text-align-center">Hello</p>' ),
);
echo render_block( $block );

---

do_blocks()

Parses dynamic blocks and re-renders them.

do_blocks( string $content ): string

Parameters:

• $content (string) – Post content

Returns: (string) – Updated post content with blocks rendered

Since: 5.0.0

Note: This is hooked to the_content filter at priority 9.

---

Block Serialization

serialize_block()

Returns the content of a block including comment delimiters.

serialize_block( array $block ): string

Parameters:

• $block (array) – Parsed block array

Returns: (string) – Serialized block markup

Since: 5.3.1

Example:

$block = array(
    'blockName'    => 'core/paragraph',
    'attrs'        => array(),
    'innerBlocks'  => array(),
    'innerHTML'    => '<p>Hello</p>',
    'innerContent' => array( '<p>Hello</p>' ),
);
echo serialize_block( $block );
// Output: <!-- wp:paragraph --><p>Hello</p><!-- /wp:paragraph -->

---

serialize_blocks()

Returns the aggregate serialization of parsed blocks.

serialize_blocks( array[] $blocks ): string

Parameters:

• $blocks (array[]) – Array of parsed block structures

Returns: (string) – Serialized markup

Since: 5.3.1

---

serialize_block_attributes()

Serializes block attributes to JSON format for block comments.

serialize_block_attributes( array $block_attributes ): string

Parameters:

• $block_attributes (array) – Attributes object

Returns: (string) – JSON-encoded string with escaped characters

Since: 5.3.1

---

get_comment_delimited_block_content()

Returns content with block comment delimiters.

get_comment_delimited_block_content(
    string|null $block_name,
    array $block_attributes,
    string $block_content
): string

Parameters:

• $block_name (string|null) – Block name (null for classic/freeform)
• $block_attributes (array) – Block attributes
• $block_content (string) – Block inner content

Returns: (string) – Comment-delimited block content

Since: 5.3.1

---

strip_core_block_namespace()

Removes the core/ namespace prefix from block names.

strip_core_block_namespace( string|null $block_name = null ): string

Parameters:

• $block_name (string|null) – Original block name

Returns: (string) – Block name without core/ prefix

Since: 5.3.1

---

Block Styles

register_block_style()

Registers a new block style.

register_block_style(
    string|string[] $block_name,
    array $style_properties
): bool

Parameters:

• $block_name (string|string[]) – Block type name(s) including namespace
• $style_properties (array) – Style properties:
  • name (string) – Style identifier
  • label (string) – Human-readable label
  • style_handle (string) – Stylesheet handle to enqueue
  • inline_style (string) – Inline CSS
  • style_data (array) – theme.json-like data for CSS generation
  • is_default (bool) – Whether this is the default style

Returns: (bool) – True on success

Since: 5.3.0
Since: 6.6.0 – Added support for multiple block types

Example:

register_block_style( 'core/quote', array(
    'name'         => 'fancy',
    'label'        => 'Fancy Quote',
    'inline_style' => '.is-style-fancy { border-left: 4px solid gold; }',
) );

// Register for multiple blocks
register_block_style(
    array( 'core/paragraph', 'core/heading' ),
    array(
        'name'  => 'gradient-text',
        'label' => 'Gradient Text',
    )
);

---

unregister_block_style()

Unregisters a block style.

unregister_block_style( string $block_name, string $block_style_name ): bool

Parameters:

• $block_name (string) – Block type name
• $block_style_name (string) – Style name

Returns: (bool) – True on success

Since: 5.3.0

---

Block Support Utilities

block_has_support()

Checks whether a block type supports a feature.

block_has_support(
    WP_Block_Type $block_type,
    string|array $feature,
    mixed $default_value = false
): bool

Parameters:

• $block_type (WP_Block_Type) – Block type to check
• $feature (string|array) – Feature slug or path
• $default_value (mixed) – Fallback value

Returns: (bool) – Whether the feature is supported

Since: 5.8.0
Since: 6.4.0 – $feature accepts string

Example:

$block_type = WP_Block_Type_Registry::get_instance()->get_registered( 'core/paragraph' );

if ( block_has_support( $block_type, 'color' ) ) {
    // Block supports color
}

if ( block_has_support( $block_type, array( 'typography', 'fontSize' ) ) ) {
    // Block supports font size
}

---

get_block_wrapper_attributes()

Generates HTML attributes string for block wrapper.

get_block_wrapper_attributes( string[] $extra_attributes = array() ): string

Parameters:

• $extra_attributes (string[]) – Extra attributes to merge

Returns: (string) – HTML attribute string

Since: 5.6.0

Example:

function render_my_block( $attributes ) {
    $wrapper_attributes = get_block_wrapper_attributes( array(
        'class' => 'my-custom-class',
    ) );
    return sprintf( '<div %s>Content</div>', $wrapper_attributes );
}

---

Block Hooks

get_hooked_blocks()

Retrieves block types hooked into given blocks.

get_hooked_blocks(): array[]

Returns: (array[]) – Hooked blocks grouped by anchor block and position

Since: 6.4.0

---

get_dynamic_block_names()

Returns names of all registered dynamic block types.

get_dynamic_block_names(): string[]

Returns: (string[]) – Array of dynamic block names

Since: 5.0.0

---

Block Editor

get_default_block_categories()

Returns default block categories.

get_default_block_categories(): array[]

Returns: (array[]) – Array of category definitions

Since: 5.8.0

Categories: text, media, design, widgets, theme, embed, reusable

---

get_block_categories()

Returns all block categories for the editor.

get_block_categories( WP_Post|WP_Block_Editor_Context $post_or_context ): array[]

Parameters:

• $post_or_context – Post object or block editor context

Returns: (array[]) – Block categories

Since: 5.0.0
Since: 5.8.0 – Accepts WP_Block_Editor_Context

---

get_allowed_block_types()

Gets list of allowed block types for the editor.

get_allowed_block_types( WP_Block_Editor_Context $context ): bool|string[]

Parameters:

• $context (WP_Block_Editor_Context) – Editor context

Returns: (bool|string[]) – Array of block slugs, or boolean to enable/disable all

Since: 5.8.0

---

get_block_editor_settings()

Returns contextualized block editor settings.

get_block_editor_settings(
    array $custom_settings,
    WP_Block_Editor_Context $context
): array

Parameters:

• $custom_settings (array) – Custom settings to merge
• $context (WP_Block_Editor_Context) – Editor context

Returns: (array) – Editor settings

Since: 5.8.0

---

Utility Functions

block_version()

Returns the block format version of content.

block_version( string $content ): int

Parameters:

• $content (string) – Content to test

Returns: (int) – 1 if content has blocks, 0 otherwise

Since: 5.0.0

---

excerpt_remove_blocks()

Parses blocks and renders only those appropriate for excerpts.

excerpt_remove_blocks( string $content ): string

Parameters:

• $content (string) – Content to parse

Returns: (string) – Filtered content

Since: 5.0.0

---

filter_block_content()

Filters and sanitizes block content to remove non-allowable HTML.

filter_block_content(
    string $text,
    array[]|string $allowed_html = 'post',
    string[] $allowed_protocols = array()
): string

Parameters:

• $text (string) – Text with block content
• $allowed_html (array[]|string) – Allowed HTML or context name
• $allowed_protocols (string[]) – Allowed URL protocols

Returns: (string) – Filtered content

Since: 5.3.1

---

traverse_and_serialize_blocks()

Traverses parsed blocks and applies callbacks during serialization.

traverse_and_serialize_blocks(
    array[] $blocks,
    callable $pre_callback = null,
    callable $post_callback = null
): string

Parameters:

• $blocks (array[]) – Parsed blocks
• $pre_callback (callable) – Called before each block
• $post_callback (callable) – Called after each block

Returns: (string) – Serialized markup

Since: 6.4.0

---

resolve_pattern_blocks()

Replaces pattern blocks with their content.

resolve_pattern_blocks( array $blocks ): array

Parameters:

• $blocks (array) – Array of blocks

Returns: (array) – Blocks with patterns resolved

Since: 6.6.0

---

Asset Handling

generate_block_asset_handle()

Generates handle name for block assets.

generate_block_asset_handle(
    string $block_name,
    string $field_name,
    int $index = 0
): string

Parameters:

• $block_name (string) – Block name
• $field_name (string) – Metadata field (e.g., editorScript)
• $index (int) – Index when multiple items

Returns: (string) – Asset handle

Since: 5.5.0
Since: 6.1.0 – Added $index parameter

---

register_block_script_handle()

Finds and registers a script handle for block metadata.

register_block_script_handle(
    array $metadata,
    string $field_name,
    int $index = 0
): string|false

Parameters:

• $metadata (array) – Block metadata
• $field_name (string) – Field name
• $index (int) – Script index

Returns: (string|false) – Script handle or false

Since: 5.5.0

---

register_block_style_handle()

Finds and registers a style handle for block metadata.

register_block_style_handle(
    array $metadata,
    string $field_name,
    int $index = 0
): string|false

Parameters:

• $metadata (array) – Block metadata
• $field_name (string) – Field name
• $index (int) – Style index

Returns: (string|false) – Style handle or false

Since: 5.5.0

---

get_block_asset_url()

Gets the URL to a block asset.

get_block_asset_url( string $path ): string|false

Parameters:

• $path (string) – Normalized path to asset

Returns: (string|false) – URL or false

Since: 6.4.0

---

Query Block Helpers

build_query_vars_from_query_block()

Constructs WP_Query args from Query block properties.

build_query_vars_from_query_block( WP_Block $block, int $page ): array

Parameters:

• $block (WP_Block) – Block instance
• $page (int) – Current page number

Returns: (array) – WP_Query arguments

Since: 5.8.0

---

get_query_pagination_arrow()

Returns pagination arrow HTML for Query blocks.

get_query_pagination_arrow( WP_Block $block, bool $is_next ): string|null

Parameters:

• $block (WP_Block) – Block instance
• $is_next (bool) – Whether this is the "next" arrow

Returns: (string|null) – Arrow HTML or null

Since: 5.9.0

---

build_comment_query_vars_from_block()

Constructs comment query vars from block properties.

build_comment_query_vars_from_block( WP_Block $block ): array

Parameters:

• $block (WP_Block) – Block instance

Returns: (array) – WP_Comment_Query parameters

Since: 6.0.0