Full text search, search from multiple tables

I'm building a small ecommerce app and I'm trying to implement a full text search (product search) but having trouble where to start because the search function should search from the 3 tables. I have 3 tables named 'categories, tags and items'. Surely I can use 'LIKE' query in each table query like,

$items = items::where('item_name','LIKE', $request->search)->get();
$items = categories::where('item_name','LIKE', $request->search)->get();
$items = tags::where('item_name','LIKE', $request->search)->get();

and then merge 3 returns collections.

Is there a best way to achieve this? or any search engine extension for Laravel 5.3 that you can suggest which can cater my needs?