一次编写，随处运行

Most readers probably find themselves in a position where they already have a number of applications that run on some other database abstraction layer. Due to MDB''s heritage most PEAR DB users should find that MDB feels very similar, since the API of MDB is based on that of PEAR DB. Metabase users should find that all their favourite functions have their counterpart in MDB. The XML schema format is exactly the same as in Metabase. A complete guide to porting your existing applications to MDB is beyond the scope of this article, instead I will use this space to give some tips. If you have any specific questions feel free to email me.
大部分读者可能发现它们处于这样的境地——他们已经有了大量运行于其他数据库抽象层的程序。由于 MDB 的出身，大部分 PEAR DB 的用户应当发现 MDB 感觉上非常类似，因为 MDB 的 API 是基于 PEAR DB 的。Metabase 用户应当发现他们所有偏爱的功能都在 MDB 中有对应的东西。XML schema 格式和 Metabase 中的是一摸一样的。一个完全的指导来引导你把已经写好的程序移植到 MDB 中超出了本文的范围，但是我将利用这个机会给一些提示。如果你有任何具体的问题，放心的发信来询问我。

To port your PEAR DB application to MDB the best place to start is the PEAR wrapper. For one you can run your application using the PEAR wrapper. The wrapper of course does add a little bit of overhead so you will probably want to port to the native interface at some point. The first step then should be listing all PEAR DB methods that your application currently uses. Then look at the wrapper for any differences in the API. There are two key differences you will notice: result sets are not objects anymore and all of the querying methods allow you to pass the data types of the result set which will result in slight changes in the parameter order. The first difference means that instead of calling the fetch method on the result object:
为了把你的 PEAR DB 程序移植到 MDB，最好的起点是 PEAR wrapper。你能使用 PEAR wrapper 来运行你的程序。wrapper 当然增加了一些额外负担，因而你可能有些想要移植到原生的接口。那么第一步是列出所有你程序当前使用的 PEAR DB 函数。然后看看 wrapper 从中找出任何 API 上的区别。有两个你要注意的关键区别：结果集不再是对象而且所有的允许你传递结果集的数据类型的查询方法将导致参数顺序上的少许改变。第一个区别意味着不能再结果对象上调用获取函数。

$result = $db->query($sql);
$row = $result->fetchRow();

You will now have to call the MDB object for fetching:
你现在必须调用 MDB 对象来进行获取：

$result = $mdb->query($sql);
$row = $mdb->fetchRow($result);

The second difference is quite easily fixed by looking at the wrapper. As you can see in the wrapper you may simply pass NULL where MDB would otherwise expect data types in the result set. Now, your application should work with MDB. Of course, you are now not really taking advantage of the advanced features of MDB. This most likely will require some changes to your current database schema. The manager can attempt to reverse engineer an X

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