Thanks teseo, that was super easy actually... this is fantastic.
I also have 2 more questions: how to add vehicle type? I tried adding $car_data['fk_vehicle_type_id'] at the end as you said, but the info shows a number only. Also, I noticed that every time the ad is updated, the information gets added again. Is it possible to make this tweak delete the old added string and replace it with the new one? Because it gets me thinking that this information after maybe some changes or updates the first values will be obsolete, but still searchable.
For example, one of the fields I added was color: so let's say user adds 2014 Ford Mustang Blue, and then realizes is not blue, so changes color to White. At this time, description would have something like this \n\0x07\0x12 Ford Mustang 2014 13 Blue\n\0x07\0x12 Ford Mustang 2014 13 White; where if someone searches for a blue Camaro, the white Mustang will be shown as well.
Thanks again!