function update error

 public function update($table, $parameters)
    {
        $sql = sprintf('update %s set %s = "%s" ', $table,implode(' ',array_keys($parameters)), ':'.implode(', ',array_keys($parameters))
            );

        try {
            $stmt = $this->pdo->prepare($sql);
            $stmt->execute($parameters);
            return true;
        } catch (\Exception $e) {
            echo $e->getMessage();
            return false;
        }
    }

Error : Warning: PDOStatement::execute(): SQLSTATE[HY093]: Invalid parameter number: number of bound variables does not match number of tokens in E:\XAM\htdocs\pdomaster\database\QueryBuilder.php on line 66