Laravel Eloquent Select CASE?
Move your raw() call inside the SELECT statement:
->select('shares.id AS share_id', 'users.id AS user_id', 'shares.connected_user_id', 'shares.original_language_id', 'shares.image', 'users.first_name', 'users.last_name', 'users.email', 'locations.city', 'provinces.name', 'countries.code', 'locations.lat', 'locations.lng', 'shares.created_at', DB::raw('(CASE WHEN users.id = ' . $user . ' THEN 1 ELSE 0 END) AS is_user') )->orderBy('shares.created_at', 'desc')
Alternatively you can use selectRaw instead.
->selectRaw("shares.id AS share_id, users.id AS user_id , shares.connected_user_id , shares.original_language_id, shares.image, users.first_name, users.last_name, users.email, locations.city, provinces.name, countries.code, locations.lat, locations.lng, shares.created_at, (CASE WHEN users.id = {$user} THEN 1 ELSE 0 END) AS is_user)") ->orderBy('shares.created_at', 'desc')