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 改為false即可解決這個問題。不過從PHPUNIT開發小組成員的建議來看，他們是不支持用修改backupGlobals的值來解決這個問題的。

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.

所以更好的解決方法就是在：

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

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

SmartPHP_Db_Table::setDefaultAdapter($db);

這段代碼之后，再添加一句：

unset($db);

這樣子就完美解決了You cannot serialize or unserialize PDO instances這個問題。