bool
mysql_stmt_close(MYSQL_STMT *stmt)
          Closes the prepared statement.
          mysql_stmt_close() also
          deallocates the statement handler pointed to by
          stmt, which at that point becomes invalid
          and should no longer be used. For a failed
          mysql_stmt_close() call, do
          not call mysql_stmt_error(),
          or mysql_stmt_errno(), or
          mysql_stmt_sqlstate() to
          obtain error information because
          mysql_stmt_close() makes the
          statement handler invalid. Call
          mysql_error(),
          mysql_errno(), or
          mysql_sqlstate() instead.
        
If the current statement has pending or unread results, this function cancels them so that the next query can be executed.
- 
The MySQL server has gone away. 
- 
An unknown error occurred. 
See the Example in Section 6.4.11, “mysql_stmt_execute()”.