user_id  name  phone
--------------------
1        john  123
2        kevin 456

car_id   nr    brand
--------------------
1        666   Ford
2        999   Dodge

log_id  car_id  user_id1 user_id2
---------------------------------
1       1       1        2

SELECT log.*, cars.*, users.*
FROM log
LEFT JOIN cars ON log.car_id=car.car_id
LEFT JOIN users ON log.user_id1=users.user_id
LEFT JOIN users ON log.user_id2=users.user_id

echo $row["brand"];
echo $row["name"]; // user_id1
echo $row["name"]; // user_id2