php sort hight to low

$letters=array("b","a","c");
arsort($letters); //referse sort an array ("c","a","b")

<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");
asort($fruits);
foreach ($fruits as $key => $val) {
    echo "$key = $val\n";
}
?>
//Would output:
c = apple
b = banana
d = lemon
a = orange  

// array sort php
$room_details = array(
      "2020-09-27": [
                {
                    "content": "how are you",
                    "detail_id": "1",
                    "time": "17:57:28",
                    "chat_time": "2020-09-24 17:57:28",
                    "width": "0",
                    "height": "0",
                    "type": "1",
                    "distance_time": "26 days ago",
                    "avatar": "uploads/MemberImage/20200922-1436-image-5f699b536f438-0.png",
                    "position": 2
                },
                {
                    "content": "I am fine, thanks",
                    "detail_id": "2",
                    "time": "17:57:45",
                    "chat_time": "2020-09-24 17:57:45",
                    "width": "0",
                    "height": "0",
                    "type": "1",
                    "distance_time": "26 days ago",
                    "avatar": "uploads/MemberImage/20200922-1436-image-5f699b536f438-0.png",
                    "position": 2
                },
      ],
	 "2020-09-24": [
                {
                    "content": "how are you",
                    "detail_id": "1",
                    "time": "17:57:28",
                    "chat_time": "2020-09-24 17:57:28",
                    "width": "0",
                    "height": "0",
                    "type": "1",
                    "distance_time": "26 days ago",
                    "avatar": "uploads/MemberImage/20200922-1436-image-5f699b536f438-0.png",
                    "position": 2
                },
                {
                    "content": "I am fine, thanks",
                    "detail_id": "2",
                    "time": "17:57:45",
                    "chat_time": "2020-09-24 17:57:45",
                    "width": "0",
                    "height": "0",
                    "type": "1",
                    "distance_time": "26 days ago",
                    "avatar": "uploads/MemberImage/20200922-1436-image-5f699b536f438-0.png",
                    "position": 2
                },
      ],
);

sort($room_details);

// result
// array sort php
$room_details = array(
      "2020-09-24": [
                ...
      ],
	 "2020-09-27": [
               ...
      ],
);