Saving a game: PHP or XML?

I’m currently making a pretty ambitious RPG, an was wondering if any of you could give me advice on an important subject: What to use to store the saved game data?

The problem that I have is that the game involves a LOT of data being saved, inc charecter details, locations, things picked up, people talked to, quests underway. I’m also making it so that it looks to see if it needs to place objects in the map, so if youv’e visted there before, its as you left it.

So, should I use PHP, or go with XML?

Thanks,

Tjomas