(PECL maxdb >= 1.0)
maxdb_stmt_close -- maxdb_stmt::close — Closes a prepared statement
过程化风格
$stmt
   ) : bool面向对象风格
   Closes a prepared statement. maxdb_stmt_close() also deallocates the
   statement handle pointed to by stmt.
   If the current statement has pending or unread results, this function cancels them so that
   the next query can be executed.
  
   成功时返回 TRUE, 或者在失败时返回 FALSE。