Function and usage of register_block_style() in wordpress


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    The register_block_style() function in WordPress is used to register new block styles for the Gutenberg editor. This function enhances the customization capabilities of blocks by allowing you to define additional styles that can be applied to blocks in the editor.

    Function Signature:

    register_block_style( string $block_name, array $style_properties ): bool


    1. $block_name (string, required): This parameter specifies the block type name, including its namespace. The namespace is generally a prefix that identifies the block. For example, for core WordPress blocks, the namespace is core/.

    2. $style_properties (array, required): An associative array containing the properties of the style. These properties include:

      • name: A unique identifier for the style.
      • label: A human-readable label for the style, which will be shown in the block editor.
      • style_handle (optional): The name of the stylesheet to be enqueued if the style requires an external stylesheet.
      • inline_style (optional): A string containing CSS code to be added directly to the page when this style is used.

    Return Value:

    • bool: Returns true if the block style was registered successfully, and false otherwise.

    Sample Usage:

    Here's an example of how you might use register_block_style() in a WordPress theme or plugin:

    function my_custom_block_styles() {
            'core/paragraph', // Block type
                'name'         => 'fancy-paragraph',
                'label'        => 'Fancy Paragraph',
                'style_handle' => 'my-custom-styles', // Handle of the registered stylesheet
                'inline_style' => 'p.fancy-paragraph { font-style: italic; color: purple; }',
    add_action( 'init', 'my_custom_block_styles' );

    In this example, a new style called "Fancy Paragraph" is registered for the core paragraph block. This style applies italic font style and purple color to the paragraph. The style can be selected from the block editor when editing a paragraph block.


    • It's important to ensure that your theme or plugin properly enqueues any stylesheets referenced by style_handle.
    • This function should be hooked to the init action, as shown in the example, to ensure it's registered early in the WordPress load process.
    • Inline styles added through inline_style are printed directly in the page's HTML, so use them judiciously to avoid excessive inline CSS.

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