Objects using PDO objects in sessions

Havin_it

Hello,

I've just been playing around with turning one of my existing scripts into Object-oriented code. The main class's constructor populates the class with data using a PDO connection, and this connection might be different for each instance.

I want to persist my objects across a session, but it seems from my efforts that it's not possible to persist the PDO objects (which I'd intended to have a reference to as an instance member of the class). Is this impossible, or is there some clever way of doing it that I'm missing? Even if I don't rewrite my scripts in full OOP style, this ability would be useful to me.

MarkR

You can't persist anything which has native resources associated with it. This includes (all?) PDO objects.

Consider using a different architecture. What PDO objects are you trying to persist? You need to create a new connection on each page anyway, so that may as well be a global, static or singleton or something.

Mark

Havin_it

Hi, thanks for the quick response =)

I thought that would be the reason, just couldn't find a definitive answer and wanted to be sure. I've been reading a bit more since I posted, and I think maybe I could compromise by keeping the PDO reference as a member, but extending the sleep and wakeup functions in my class to drop and re-create the reference from one page to the next.

The different PDO objects are connections to different databases. A parameter passed to my class's constructor tells it which database it needs to connect to. The constructor then calls an external function that returns the PDO object for the requested database (as well as creating that object, and even creating the database, if necessary).

Sorry, but your terminology at the end of your last para lost me completely (showing my lack of experience I fear). Could you elaborate?

Havin_it

Solution arrived at. I added connect() and disconnect() methods to my class, which (respectively) call the external function to get a reference to the correct database, and dereference it. The other methods that include queries (including the constructor, which I didn't think would be possible) call these functions so the connection is only referenced when needed. As a safety-net, I added a __sleep() method that calls disconnect() in case the DB hasn't been dereferenced.

I didn't need to make an equivalent __wakeup() method, and I found that this would have been hard anyway, as my original intended method would have made use of other session vars.

This leads me to a secondary question: Is there an ordering of session variables, such that you could ensure that one var had 'woken up' before another one which could then access it in its own __wakeup() function? If anyone knows, I'd be interested.