Is it common practice to keep PHP objects alive by storing them in session variables?

I'm new to OOP using PHP and the idea seems a little pointless in some ways. In non-webbased languages the object lives through-out the life of the program (from execution to exit). In this situation it make perfect sense because you build the开发者_运维问答 class then initialize it at run-time where you can access it frequently as needed there after. However with web programming since the execution of an application might happen in many stages (page loads) the life of the object could end up being only a small portion of the time an application is being run. So it seems to me that the only option to keep objects alive during the course of the application's usage would be to store that object after initialization in a session variable. Is this common practice or are there other means by which to utilize the power of OOP in PHP more effectively?

PHP's website has an article that deals specifically with this: Serializing objects - objects in sessions. There's absolutely nothing wrong with serialize objects in your session but as this article suggests:

It is strongly recommended that if an application serializes objects, for use later in the application, that the application include the class definition for that object throughout the application. Not doing so might result in an object being unserialized without a class definition...

It can still be very useful to manage objects with short, time-limited lifespans. Perhaps you want to communicate with two different kinds of database servers -- having objects that know how to build queries for those database servers can be very convenient. You, the programmer, get to interact with them in the same way, but behind the scenes one might use a unix domain socket to talk with a local PostgreSQL and the other might use a TCP connection from a session pool to talk with an Oracle instance.

Object-oriented programming exist to provide encapsulation and abstraction. Both are useful, even if the objects involved are created, live, and die, in .5 seconds.

With PHP you cannot keep an object alive, so you cannot store it in the session to gain performance. PHP will always serialize the object when writing to the session and deserialize it reading from the session.

To answer your question, yes it's very common to store an object in a session, but not for performance reasons. Storing and reading from the session are quiet fast, so i would only look for optimizations there, if you are sure this is a bottleneck.

Somethings to make sure you do if you take this approach is make sure your garbage collection is thoroughly working. Depending on what the object does it may store as quite a large record in which case you will be taking up quite a bit of disk/database storage.

I am a Codeigniter fan but those objects are huge and it would be highly unwise to store them. Security is another factor - if you are on a shared server and there is a chance of security credentials being held in the object then storing these may also be unwise.

I do store objects in a database but just make sure Garbage collection is working. If you use a database there is a bug in Ubuntu where the collection doesn't run - in which case you need to force it through ini_set.