Serializing Objects

[DeadFly]

Hey everyone . . .
I've been recently learning about OOP and PHP (using classes ans whatnot), and I've stumbled upon something I'm having trouble understanding . . . serializing objects.

I've read the manual, and the downloadable PHP help file (basically the same thing), and I still don't quite understand it. Maybe I'm just missing something when I'm reading it ? ? ?

"serialize() returns a string containing a byte-stream representation of any value that can be stored in PHP. unserialize() can use this string to recreate the original variable values. Using serialize to save an object will save all variables in an object. The functions in an object will not be saved, only the name of the class." -PHP manual

Can someone help me understand it a bit ?
What is the purpose of serializing objects ?

[ereptur]

The use that I have put to serializing objects is for storage from page to page i.e. with sessions/cookies.

On my forum site, when a user logs in or has a cookie with login data, the scripts will detect this and extract from the session variable the user object. When doing this, it saves me from having to make a query to the database each time a page is loaded thus saving on processor utilization (and bandwidth utilization should the database be located on a remote server).

Without serializing the object before storing it in a session variable, I believe that the contents are not stored properly, thus causing erratic behaviour.