public function delete()
 {
     Shared_With::delete_content($this->content_id);
     Like::delete_content($this->content_id);
     Comment::delete_content($this->content_id);
     global $database;
     $sql = "DELETE FROM " . self::$table_name . " ";
     $sql .= "WHERE content_id=" . $database->escape_value($this->content_id);
     $sql .= " LIMIT 1";
     $database->query($sql);
     return $database->affected_rows() == 1 ? true : false;
 }