这是个在别人的基础上做修改的代码，添加了 判断单元格值是否为数值，是的话，将该单元格的类型转成 Number，避免生产的EXCEL中没法进行数值的加减。。。
<?php
/**
* Simple excel generating from PHP5
*
* This is one of my utility-classes.
*
* The MIT License
*
* Copyright (c) 2007 Oliver Schwarz
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* from, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* @package Utilities
* @author Oliver Schwarz <oliver.schwarz@gmail.com>
* @version 1.0
*/
/**
* Generating excel documents on-the-fly from PHP5
*
* Uses the excel XML-specification to generate a native
* XML document, readable/processable by excel.
*
* @package Utilities
* @subpackage Excel
* @author Oliver Schwarz <oliver.schwarz@vaicon.de>
* @version 1.0
*
* @todo Add error handling (array corruption etc.)
* @todo Write a wrapper method to do everything on-the-fly
*/
class MyClass_ExcelXML
{
/**
