code: public function set_posts_to_review() {
  
  		$total_posts = wp_count_posts();
  		$total_posts = isset( $total_posts->publish ) ? $total_posts->publish : 0;
  
  		$posts = get_posts(
  			[
  				'post_type'   => 'post',
  				'numberposts' => $total_posts,
  				'post_status' => 'publish',
  			]
  		);
  
  		foreach ( $posts as $post ) {
  			if ( isset( $post->ID ) ) {
  				add_post_meta(
  					$post->ID,
  					'custom_images_grifus',
  					'false',
  					true
  				);
  			}
  		}
  	}
docs: Set posts to review.