Gutenberg Reusable Blocks

functions.php

<?php

final class WP_Gutenberg_Reusable_Blocks_Widgets {
	private static $instance;

	public static function instance() {
		if ( ! isset( self::$instance ) && ! ( self::$instance instanceof WP_Gutenberg_Reusable_Blocks_Widgets ) ) {
			self::$instance = new WP_Gutenberg_Reusable_Blocks_Widgets;

			self::$instance->initing();
		}

		return self::$instance;
	}

	private function initing() {
		add_action( 'widgets_init', function () {
			register_widget( 'GUTENRBW_WIDGET' );
		} );
	}

}

add_action( 'after_setup_theme', 'GutenReusableBlocksWidgets', 90 );
function GutenReusableBlocksWidgets() {
	return WP_Gutenberg_Reusable_Blocks_Widgets::instance();
}


function gutenrbw_global_blocks() {
	global $wpdb;

	$blocks = $wpdb->get_results( "SELECT ID, post_title, post_parent FROM $wpdb->posts WHERE post_type = 'wp_block' AND post_status = 'publish' ORDER BY post_title ASC " );
	update_option( 'gutenberg_reusable_blocks_widgetopts', $blocks );

	return apply_filters( 'gutenberg_reusable_blocks_widget_get', $blocks );
}

class GUTENRBW_WIDGET extends WP_Widget {
	public function __construct() {
		$widget_ops = array(
			'classname'   => 'gutenberg-reusable-widget',
			'description' => __( 'Display Gutenberg Reusable saved Blocks anywhere as widget.', 'gold' ),
		);
		parent::__construct( 'gutenrbw_widget', __( 'Reusable Block', 'gold' ), $widget_ops );
	}

	public function widget( $args, $instance ) {
		if ( isset( $instance['block'] ) && ! empty( $instance['block'] ) ) {
			echo $args['before_widget'];
			if ( ! empty( $instance['title'] ) ) {
				echo $args['before_title'] . apply_filters( 'widget_title', $instance['title'] ) . $args['after_title'];
			}
			echo apply_filters( 'the_content', get_post_field( 'post_content', $instance['block'] ) );
			echo $args['after_widget'];
		}
	}

	public function form( $instance ) {
		$title          = ! empty( $instance['title'] ) ? $instance['title'] : '';
		$block_selected = ! empty( $instance['block'] ) ? $instance['block'] : '';
		$blocks         = gutenrbw_global_blocks(); ?>
		<p>
			<label for="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"><?php esc_attr_e( 'Title:', 'gold' ); ?></label>
			<input class="widefat" id="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"
			       name="<?php echo esc_attr( $this->get_field_name( 'title' ) ); ?>" type="text"
			       value="<?php echo esc_attr( $title ); ?>">
		</p>
		<?php if ( ! empty( $blocks ) ) { ?>
			<p>
				<label for="<?php echo esc_attr( $this->get_field_id( 'block' ) ); ?>"><?php _e( 'Choice from saved Reusable Blocks:', 'gold' ); ?></label>
				<select class="widefat" id="<?php echo esc_attr( $this->get_field_id( 'block' ) ); ?>"
				        name="<?php echo esc_attr( $this->get_field_name( 'block' ) ); ?>">
					<option values=""><?php _e( 'Select Reusable Block', 'gold' ); ?></option>
					<?php foreach ( $blocks as $block ) {
						$selected = ( $block_selected == $block->ID ) ? 'selected="selected"' : ''; ?>
						<option value="<?php echo $block->ID; ?>" <?php echo $selected; ?>><?php echo $block->post_title; ?></option>
					<?php } ?>
				</select>
			</p>
			<?php
		} else { ?>
			<p><?php _e( 'No saved reusable blocks yet.', 'gold' ); ?></p>
		<?php }
	}

	public function update( $new_instance, $old_instance ) {
		$instance          = array();
		$instance['title'] = ( ! empty( $new_instance['title'] ) ) ? strip_tags( $new_instance['title'] ) : '';
		$instance['block'] = ( ! empty( $new_instance['block'] ) ) ? strip_tags( $new_instance['block'] ) : '';

		return $instance;
	}
}

//How to use
require_once(get_template_directory().'/inc/reusable-block-widgets.php');
add_action('admin_menu', function(){
	add_menu_page(
		'Gutenberg Reusable Blocks',
		'Gutenberg Reusable Blocks',
		'manage_options',
		'/edit.php?post_type=wp_block',
		'',
		'dashicons-portfolio',
		81
	);
} );