serialize_block( array $block ): string

Returns the content of a block, including comment delimiters, serializing all attributes from the given parsed block.


This should be used when preparing a block to be saved to post content.
Prefer render_block when preparing a block for display. Unlike render_block, this does not evaluate a block’s render_callback, and will instead preserve the markup as parsed.


A representative array of a single parsed block object. See WP_Block_Parser_Block.
  • blockName string
    Name of block.
  • attrs array
    Attributes from block comment delimiters.
  • innerBlocks array[]
    List of inner blocks. An array of arrays that have the same structure as this one.
  • innerHTML string
    HTML from inside block comment delimiters.
  • innerContent array
    List of string fragments and null markers where inner blocks were found.


string String of rendered HTML.


function serialize_block( $block ) {
	$block_content = '';

	$index = 0;
	foreach ( $block['innerContent'] as $chunk ) {
		$block_content .= is_string( $chunk ) ? $chunk : serialize_block( $block['innerBlocks'][ $index++ ] );

	if ( ! is_array( $block['attrs'] ) ) {
		$block['attrs'] = array();

	return get_comment_delimited_block_content(



User Contributed Notes

  1. Skip to note 2 content

    A sample code to understand how this works. I am using to execute this.

     * Create a block programmatically and serialize it.
    $block_name = 'core/paragraph';
    $innerHTML  = 'Sample paragraph text.';
    $converted_block = new WP_Block_Parser_Block( $block_name, array(), array(), $innerHTML, array( $innerHTML ) );
    WP_CLI::log( print_r( $converted_block, true ) );
    $serialized_block = serialize_block( (array) $converted_block );
    WP_CLI::log( $serialized_block );

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