Laravel query left join

I have a self referencing table with parent id and a child category_id, this query works has SQL:

SELECT a.id, a.name, b.name, a.created_at
            FROM shop_categories a
            LEFT JOIN shop_categories b ON (a.id = b.category_id)
            WHERE a.category_id = 0

And I'm trying to translate this to Laravel Query Builder language, I managed to come up with this, but it does not work, and I don't know what I'm doing wrong, my laravel query:

$shopcategories = DB::table('shop_categories as a')
            ->select('a.id', 'a.name','b.name','a.created_at')
            ->leftJoin('shop_categories as b', function ($join) {
                $join->on('a.id', '=', 'b.category_id');
            })
            ->where('a.category_id', '=', 0)
            ->get();

Thanks in advance.

via Chebli Mohamed