I don\'t want to create a discussion about singleton better than static or better than global, etc. I read dozens of questions about similar subjects on SO, but I couldn\'t
Making DB library static is certainly shorter and quicker, than doing:
$db = DBSingleton::blabla(); // everytime I need ya
But also, since it is global, tempting to use everywhere.
So, choose other methods if you want clean code... and choose static if you need quick code ;-)