code: public function restart_all_ratings() {
  
  		$nonce = isset( $_POST['nonce'] ) ? $_POST['nonce'] : '';
  
  		if ( ! wp_verify_nonce( $nonce, 'eliasis' ) && ! wp_verify_nonce( $nonce, 'customRatingGrifusAdmin' ) ) {
  			die( 'Busted!' );
  		}
  
  		$response['ratings_restarted'] = 0;
  
  		$posts = $this->model->get_posts();
  
  		foreach ( $posts as $post ) {
  			if ( isset( $post->ID ) && ! $this->model->get_movie_votes( $post->ID ) ) {
  				$this->set_rating_and_votes(
  					$post->ID,
  					$this->get_default_votes( $post->ID )
  				);
  				$response['ratings_restarted']++;
  			}
  		}
  
  		echo json_encode( $response );
  
  		die();
  	}
docs: Restart all ratings.