So I'm designing a reporting system at work it's my first project written OOP and I'm stuck on the design choice for the DB class.
Obviously I only want to create one instance of the DB class per-session/user and then pass it to each of the classes that need it. What I don't know it what's best practice for implementing this. Currently I have code like the following:-

class db
{
    private $user = 'USER';
    private $pass = 'PASS';
    private $tables = array( 'user','report', 'etc...');

    function __construct(){
        //SET UP CONNECTION AND TABLES
    }
};

class report{
function __construct ($params = array(), $db, $user)
 {        
    //Error checking/handling trimed
    //$db is the database object we created
    $this->db = $db;

    //$this->user is the user object for the logged in user
    $this->user = $user;

    $this->reportCreate();
 }

public function setPermission($permissionId = 1)
{
    //Note the $this->db is this the best practise solution?
   $this->db->permission->find($permissionId)

    //Note the $this->user is this the best practise solution?        
    $this->user->checkPermission(1)

    $data=array();
    $this->db->reportpermission->insert($data)
}
};//end report

I've been reading about using static classes and have just come across Singletons (though these appear to be passé already?) so what's current best practice for doing this?