PHP: Storing ‘objects’ inside the $_SESSION


I just figured out that I can actually store objects in the $_SESSION and I find it quite cool because when I jump to another page I still have my object. Now before I start using this approach I would like to find out if it is really such a good idea or if there are potential pitfalls involved.

I know that if I had a single point of entry I wouldn't need to do that but I'm not there yet so I don't have a single point of entry and I would really like to keep my object because I don't lose my state like that. (Now I've also read that I should program stateless sites but I don't understand that concept yet.)

So in short: Is it ok to store objects in the session, are there any problems with it?


Temporary summary: By now I understand that it is probably better to recreate the object even if it involves querying the database again.

Further answers could maybe elaborate on that aspect a bit more!

Best Solution

I know this topic is old, but this issue keeps coming up and has not been addressed to my satisfaction:

Whether you save objects in $_SESSION, or reconstruct them whole cloth based on data stashed in hidden form fields, or re-query them from the DB each time, you are using state. HTTP is stateless (more or less; but see GET vs. PUT) but almost everything anybody cares to do with a web app requires state to be maintained somewhere. Acting as if pushing the state into nooks and crannies amounts to some kind of theoretical win is just wrong. State is state. If you use state, you lose the various technical advantages gained by being stateless. This is not something to lose sleep over unless you know in advance that you ought to be losing sleep over it.

I am especially flummoxed by the blessing received by the "double whammy" arguments put forth by Hank Gay. Is the OP building a distributed and load-balanced e-commerce system? My guess is no; and I will further posit that serializing his $User class, or whatever, will not cripple his server beyond repair. My advice: use techniques that are sensible to your application. Objects in $_SESSION are fine, subject to common sense precautions. If your app suddenly turns into something rivaling Amazon in traffic served, you will need to re-adapt. That's life.