php - Rewrite URL based on variable -

i need add variable of username of url's when user logged in.

so example be:

• www.example.com/?user=user1
• www.example.com/category1/product1/?user=user1

the reason need add variable sending page pdf service each user has unique style template.

i have variable set how can rewrite page url include variable if isn't included on url using php?

apache can't know if user logged in, concerns php code. in case, think best solution add session variable :

$_session['user'] = 'user1'; 

and instead of check if user parameter exists, have check if $_session['user'] exists. easier , safer.