To store special character and other language string like german, franch
wordpress special character filter. Keep Special character into wp database.
For special Character store -
$person_typesd = [{"name": "Schüler", "count": "2", "cost": "30"}, {"name": "Schüler", "count": "34", "cost": "170"}];
json_encode($person_typesd,JSON_UNESCAPED_UNICODE)