Title: WP_Block_Bindings_Registry::register
Published: April 3, 2024
Last modified: February 24, 2026

---

# WP_Block_Bindings_Registry::register( string $source_name, array $source_properties ): 󠀁[WP_Block_Bindings_Source](https://developer.wordpress.org/reference/classes/wp_block_bindings_source/)󠁿|false

## In this article

 * [Description](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#description)
    - [See also](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#see-also)
 * [Parameters](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#parameters)
 * [Return](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#return)
 * [Source](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#source)
 * [Related](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#related)
 * [Changelog](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#changelog)

[ Back to top](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#wp--skip-link--target)

Registers a new block bindings source.

## 󠀁[Description](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#description)󠁿

This is a low-level method. For most use cases, it is recommended to use the `register_block_bindings_source()`
function instead.

### 󠀁[See also](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#see-also)󠁿

 * [register_block_bindings_source()](https://developer.wordpress.org/reference/functions/register_block_bindings_source/):
   Sources are used to override block’s original attributes with a value coming 
   from the source. Once a source is registered, it can be used by a block by setting
   its `metadata.bindings` attribute to a value that refers to the source.

## 󠀁[Parameters](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#parameters)󠁿

 `$source_name`stringrequired

The name of the source. It must be a string containing a namespace prefix, i.e.
`
my-plugin/my-custom-source`. It must only contain lowercase alphanumeric characters,
the forward slash `/` and dashes.

`$source_properties`arrayrequired

The array of arguments that are used to register a source.

 * `label` string
 * The label of the source.
 * `get_value_callback` callable
 * A callback executed when the source is processed during block rendering.
    The
   callback should have the following signature: `function( $source_args, $block_instance,
   $attribute_name ): mixed`
    - @param array $source_args Array containing source arguments used to look up
      the override value, i.e. {"key": "foo"}.
    - @param [WP_Block](https://developer.wordpress.org/reference/classes/wp_block/)
      $block_instance The block instance.
    - @param string $attribute_name The name of the target attribute.
 *  The callback has a mixed return type; it may return a string to override the
   block’s original value, null, false to remove an attribute, etc.
 * `uses_context` string[]
 * Optional. Array of values to add to block `uses_context` needed by the source.

## 󠀁[Return](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#return)󠁿

 [WP_Block_Bindings_Source](https://developer.wordpress.org/reference/classes/wp_block_bindings_source/)
|false Source when the registration was successful, or `false` on failure.

## 󠀁[Source](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#source)󠁿

    ```php
    public function register( string $source_name, array $source_properties ) {
    	if ( ! is_string( $source_name ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'Block bindings source name must be a string.' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	if ( preg_match( '/[A-Z]+/', $source_name ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'Block bindings source names must not contain uppercase characters.' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	$name_matcher = '/^[a-z0-9-]+\/[a-z0-9-]+$/';
    	if ( ! preg_match( $name_matcher, $source_name ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'Block bindings source names must contain a namespace prefix. Example: my-plugin/my-custom-source' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	if ( $this->is_registered( $source_name ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			/* translators: %s: Block bindings source name. */
    			sprintf( __( 'Block bindings source "%s" already registered.' ), $source_name ),
    			'6.5.0'
    		);
    		return false;
    	}

    	// Validates that the source properties contain the label.
    	if ( ! isset( $source_properties['label'] ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'The $source_properties must contain a "label".' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	// Validates that the source properties contain the get_value_callback.
    	if ( ! isset( $source_properties['get_value_callback'] ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'The $source_properties must contain a "get_value_callback".' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	// Validates that the get_value_callback is a valid callback.
    	if ( ! is_callable( $source_properties['get_value_callback'] ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'The "get_value_callback" parameter must be a valid callback.' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	// Validates that the uses_context parameter is an array.
    	if ( isset( $source_properties['uses_context'] ) && ! is_array( $source_properties['uses_context'] ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'The "uses_context" parameter must be an array.' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	if ( ! empty( array_diff( array_keys( $source_properties ), $this->allowed_source_properties ) ) ) {
    		_doing_it_wrong(
    			__METHOD__,
    			__( 'The $source_properties array contains invalid properties.' ),
    			'6.5.0'
    		);
    		return false;
    	}

    	$source = new WP_Block_Bindings_Source(
    		$source_name,
    		$source_properties
    	);

    	$this->sources[ $source_name ] = $source;

    	return $source;
    }
    ```

[View all references](https://developer.wordpress.org/reference/files/wp-includes/class-wp-block-bindings-registry.php/)
[View on Trac](https://core.trac.wordpress.org/browser/tags/6.9.4/src/wp-includes/class-wp-block-bindings-registry.php#L97)
[View on GitHub](https://github.com/WordPress/wordpress-develop/blob/6.9.4/src/wp-includes/class-wp-block-bindings-registry.php#L97-L193)

## 󠀁[Related](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#related)󠁿

| Uses | Description | 
| [WP_Block_Bindings_Registry::is_registered()](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/is_registered/)`wp-includes/class-wp-block-bindings-registry.php` |

Checks if a block bindings source is registered.

  | 
| [WP_Block_Bindings_Source::__construct()](https://developer.wordpress.org/reference/classes/wp_block_bindings_source/__construct/)`wp-includes/class-wp-block-bindings-source.php` |

Constructor.

  | 
| [__()](https://developer.wordpress.org/reference/functions/__/)`wp-includes/l10n.php` |

Retrieves the translation of $text.

  | 
| [_doing_it_wrong()](https://developer.wordpress.org/reference/functions/_doing_it_wrong/)`wp-includes/functions.php` |

Marks something as being incorrectly called.

  |

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## 󠀁[Changelog](https://developer.wordpress.org/reference/classes/wp_block_bindings_registry/register/?output_format=md#changelog)󠁿

| Version | Description | 
| [6.5.0](https://developer.wordpress.org/reference/since/6.5.0/) | Introduced. |

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