/**
 * Serializes a block.
 *
 * @param array $block Block object.
 * @return string String representing the block.
 */
function serialize_block( $block ) {
    if ( ! isset( $block['blockName'] ) ) {
        return false;
    }
    $name = $block['blockName'];
    if ( 0 === strpos( $name, 'core/' ) ) {
        $name = substr( $name, strlen( 'core/' ) );
    }
    if ( empty( $block['attrs'] ) ) {
        $opening_tag_suffix = '';
    } else {
        $opening_tag_suffix = ' ' . json_encode( $block['attrs'] );
    }
    if ( empty( $block['innerHTML'] ) ) {
        return sprintf(
            '<!-- wp:%s%s /-->',
            $name,
            $opening_tag_suffix
        );
    } else {
        return sprintf(
            '<!-- wp:%1$s%2$s -->%3$s<!-- /wp:%1$s -->',
            $name,
            $opening_tag_suffix,
            $block['innerHTML']
        );
    }
}