I am confused in building query for laravel .5.3?

I am using folloing table structure

resource_type 
      id
      type

communiction_links
      id
      inst_id
      rety_id
      cont_id
      value

 contact
      id
      fname
      lname
      image
      park

I want search the pattern in in two tables and retrive data from two tables. if pattern is digit then i will search in communication_links and if pattern is alphabates then i will search in contact in fname or lname column (where communication_links's cont_id and contact's id should be same) and (communication_links's rety_id and resource_type's id should be same)

i wrote down following query but i got error.

$parent_contact = \App\Contact::join('communication_links','contacts.id','=','communication_links.cont_id')
                                            ->join('resource_types','resource_types.id','=','communication_links.rety_id')
                                            ->select('contacts.id','contacts.image','contacts.fname','contacts.lname','communication_links.value')
                                            ->where('resource_types.type','LIKE',"{mobile}%")
                                            ->where(function ($query) {
                                                $query->where('communication_links.value','LIKE',"{$request->search_string}%")
                                                        ->orWhere('contacts.fname','LIKE',"{$request->search_string}%")
                                                        ->orWhere('contacts.lname','LIKE',"{$request->search_string}%");
                                            })
                                            ->get();

via Chebli Mohamed