__sleep, __wakeup and persistent connections

I'm sorting out some code to handle session object storage, particularly where the objects contain DB connections. I've found lots of articles that go on about how __sleep should clean up db stuff, close connections etc and how __wakeup should reconnect, but weirdly enough I've not found a single concrete example of doing this! It's also not quite clear how this behaviour interacts with persistent connections. For example, If I do this: class foo {

    protected $db;

    public function __construct() {
        $this->db = mysql_pconnect(....);
    }

    protected function __wakeup() {
        $this->db = mysql_pconnect(....);
    }

    protected function __sleep() {
        mysql_close($this->db);
        $this->db = NULL;
        return array();
    }

} given that the connection is persistent, and may thus be used by other scripts, is calling mysql_close a particularly bad idea? Should I just not bother closing the connection, letting PHP deal with it - the object will not attempt to re-use the stale connection because it will get a new instance courtesy of __wakeup when unserialized. I'm also unclear about how __sleep acts in subclasses - it seems that as soon as I have a __sleep function in a base class, I don't have any choice but to implement __sleep functions in every subclass of it, even if I don't want them to do anything that would not be done if __sleep were not defined. in the exampel, the base class has no properties to save, so it returns an empty array from __sleep, but that's unlikely to be useful for a subclass that does have properties (and serializing an object without any properties is pointless!). Ideas? Marcus -- Marcus Bointon Synchromedia Limited: Putting you in the picture marcus@synchromedia.co.uk | http://www.synchromedia.co.uk