Putting orderby from highest to lowest in database query - php

Question

1.I've a confusion on how to add sort orderby(highest to lowest) in my database query for the age.I've tried some few codes but it generates an error.Any help here is much appreciated.
public function ListOrgaScholar($ship_id){
$ship = Scholarship::find($ship_id);
$ship_age_from = $ship->ship_age_from;
$ship_age_to = $ship->ship_age_to;
$scholars = (new Scholar)->newQuery()->select('*');
$scholars->whereBetween(DB::raw('TIMESTAMPDIFF(YEAR,scholars.scholar_birthday,CURDATE())'),array($ship_age_from,$ship_age_to));
$scholars = $scholars->get();
}
2.Same us here.How to add orderby(highest to lowest) since it is two different where clause.The $ship_gpa_from and $ship_gpa_to are inputs of grade.
public function ListOrgaScholar($ship_id){
$ship = Scholarship::find($ship_id);
$ship_gpa_from = $ship->ship_gpa_from;
$ship_gpa_to = $ship->ship_gpa_to;
$scholars = (new Scholar)->newQuery()->select('*');
if($ship_gpa_from)
$scholars->where('scholar_GPA', '>=', $ship_gpa_from);
if($ship_gpa_to)
$scholars->where('scholar_GPA', '<=', $ship_gpa_to);
$scholars = $scholars->get();
}

Answer 1

Have you tried returning the results as collection and then applying collection functions on them? The code would look somewhat like this:
$scholarship = Scholarship::find($id);
$scholars = Scholar::all();
$selectedScholars = $scholars->filter(function ($item, $key) {
$scholarAge = Carbon::now() - $item->scholar_birthday //this depends on the value of scholar_birthday;
return ($scholarAge >= $scholarship->ship_age_from && $scholarAge <= $scholarship->ship_age_from);
})->sortBy("scholar_birthday");