I prefer to cache mostly static data (weapon stats).
I.e: weapon.arc
PHP Code:
name=whatever weapon
speed=fast
power=high
WeaponDB.weapon.loadvars("path/to/arcs/weapon.arc");
It's a lot easier to access down the run, and you won't have to update a table if you need a new variable.
But for player and item storage, SQL all the way.