Mysql insert not working properly

[eluser]ppwalks[/eluser]
Tried this way already:

Code:

$data = array(
        array(
         'product_id' => $product,
          'cat_id'  => $cat_id
         )
  );

Which Gives:

Message: Array to string conversion

Unknown column 'Array' in 'field list'

INSERT INTO `product_category` (`cat_id`, `product_id`) VALUES (Array,Array)

So as you can see it the reverse of the problem I had earlier, this way doesn't work either