input: Write a function to parse a given json-formatted string into a dictionary. If the input string is not in valid json format, return an empty dictionary. The function should be named 'parse_json_to_dict'.
  assert parse_json_to_dict('{"name": "John","age": 30,"address": {"city": "New York","state": "NY"}}')=={'name': 'John', 'age': 30, 'address': {'city': 'New York', 'state': 'NY'}}
  assert parse_json_to_dict('{"name": "Jane", "age": 25}')=={'name': 'Jane', 'age': 25}
  assert parse_json_to_dict('invalid json')=={}
  assert parse_json_to_dict('')=={}
output: try:
      import json
      return json.loads(s)
  except json.JSONDecodeError:
      return {}