phpunit遇到You cannot serialize or unserialize PDO instances

globalsBackup causes: PDOException: You cannot serialize or unserialize PDO instances。

在PHPUnit/Frameword/TestCase.php文件中，有一行protected $backupGlobals = TRUE;

把backupGlobals 改为false即可解决这个问题。不过从PHPUNIT开发小组成员的建议来看，他们是不支持用修改backupGlobals的值来解决这个问题的。

The majority of users of PHPUnit expects it to work as it does when the backup of $GLOBALSfeature is enabled. This is why it is enabled by default.

If your tests exercise code that puts unserializable objects into $GLOBALS you can disable the feature.

From a software design perspective, you should not have a global instance of PDO to begin with.

所以更好的解决方法就是在：

$db = SmartPHP_Db::factory($dbConfig);

SmartPHP_Pool::set("db" , $db);

SmartPHP_Db_Table::setDefaultAdapter($db);

这段代码之后，再添加一句：

unset($db);

这样子就完美解决了You cannot serialize or unserialize PDO instances这个问题。