Владимир

class ProductSearch extends Product
{
..........
public function search($params)
{
$query = Product::find();

$dataProvider = new ActiveDataProvider([
'query' => $query,
]);

$query->joinWith(['section' => function($query) { $query->from(['section' => 'section']); }]);
$query->joinWith(['catalog' => function($query) { $query->from(['catalog' => 'catalog']); }]);
..........
$search_array = explode(' ', $this->search_string);
$query->andFilterWhere(['OR LIKE', 'catalog.catalog_name', $search_array])
$query->andFilterWhere(['OR LIKE', 'section.section_name', $search_array])
...........
}
}