__sleep并且__wakeup是相关的序列化过程的方法。serialize函数检查类是否具有__sleep方法。如果是这样，它将在任何序列化之前执行。__sleep应该返回一个数组，该数组包含应该序列化的对象的所有变量的名称。
__wakeupunserialize如果存在于类中，则依次执行。目的是重新建立在非序列化时需要初始化的资源和其他内容。
class Sleepy {
public $tableName;
public $tableFields;
public $dbConnection;
/**
* This magic method will be invoked by serialize function.
* Note that $dbConnection is excluded.
*/
public function __sleep()
{
// Only $this->tableName and $this->tableFields will be serialized.
return ['tableName', 'tableFields'];
}
/**
* This magic method will be called by unserialize function.
*
* For sake of example, lets assume that $this->c, which was not serialized,
* is some kind of a database connection. So on wake up it will get reconnected.
*/
public function __wakeup()
{
// 连接到一些默认数据库并将存储的处理程序/包装返回
// $this->dbConnection
$this->dbConnection = DB::connect();
}
}