I am getting error in PHP script: undefined property: stdclass::$newsid"

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PHP

MySQL

Android

Hello Guys. I am working on a android project. I am beginner in Android app, php and mysql. I am getting this error: "Undefined property: stdClass::$newsId"
How can I fix this error?

I am getting error in this line:

$newsId = $request -> {'newsId'};

The whole code:

<?php
	
	include 'config/db_config.php';
	
	$data = file_get_contents("php://input");
	$request = json_decode($data);
	$response = array();
	$isValidRequest = false;
	
	//{"action":"REGISTER_USER","userName":"Mr. Amir"}
	//REGISTER_USER
	//ADD_NEWS
	//GET_NEWS
	//UPDATE_NEWS
	//DELETE_NEWS

	if(isset($request->{'action'})){
		if($request->{'action'} == 'REGISTER_USER'){
			$isValidRequest = true;
			$userName = $request -> {'userName'};

			$query = $connection->prepare("INSERT INTO user(name) VALUES (?)");
			$query->bind_param("s", $userName);
			$result = $query->execute(); 
			if($result){
				$response['userId'] = mysqli_insert_id($connection);
				$response['status'] = true; 
				$response['responseCode'] = 0; //User Registered Successfully
				$response['message'] = "User Registered Successfully";				
			}else{
				$response['status'] = false; 
				$response['responseCode'] = 102; //User Registered Failed
				$response['message'] = "User Registered Failed";				
			}
		}

		if($request->{'action'} == 'ADD_NEWS'){
			$isValidRequest = true;

			$headline = $request -> {'headline'};
			$description = $request -> {'description'};
			$userId = $request -> {'userId'};

			$query = $connection->prepare("INSERT INTO news(headline,description,user_id) VALUES (?,?,?)");
			$query->bind_param("sss", $headline, $description, $userId);
			$result = $query->execute();

			if($result){
				$response['newsId'] = mysqli_insert_id($connection);
				$response['status'] = true; 
				$response['responseCode'] = 0; //News Added Successfully
				$response['message'] = "News Added Successfully";				
			}else{
				$response['status'] = false; 
				$response['responseCode'] = 103; //News not added
				$response['message'] = "News Not Added";
			}
		}

		if($request->{'action'} == 'GET_NEWS'){
			$isValidRequest = true;

			$userId = $request -> {'userId'};
			$query = "SELECT n.id as newsId, u.id as userId, n.date_time as newsDateTime, u.date_time as userDateTime, n.*, u.* FROM news n INNER JOIN user u on n.user_id = u.id";
			$result = mysqli_query($connection, $query);

			//$query = $connection->prepare("SELECT n.id as newsId, u.id as userId, n.date_time as newsDateTime, u.date_time as userDateTime, n.*, u.* FROM news n INNER JOIN user u on n.user_id = u.id");
			//$result = $query->execute();

			if($result && mysqli_num_rows($result)>0){
				$myNews = array();
				$allNews = array();
				while(($row = mysqli_fetch_assoc($result))!=null){
					$news = array();
					$news["newsId"] = $row['newsId'];
					$news["newsBy"] = $row['name'];
					$news["headline"] = $row['headline'];
					$news["description"] = $row['description'];
					$news["dateTime"] = $row['newsDateTime'];

					$allNews[] = $news;

					if($row['userId'] == $userId){
						$myNews[] = $news;
					}
				}

				$response['status'] = true; 
				$response['responseCode'] = 0; //News are available
				$response['message'] = "News is Available";
				$response['allNews'] = $allNews;
				$response['myNews'] = $myNews;

			}else{
				$response['status'] = false; 
				$response['responseCode'] = 104; //News not available
				$response['message'] = "News Not Available";
			}
		}

		if($request->{'action'} == 'UPDATE_NEWS'){
			$isValidRequest = true;

			$userId = $request -> {'userId'};
			$headline = $request -> {'headline'};
			$description = $request -> {'description'};
			$newsId = $request -> {'newsId'};

			$query = "UPDATE news SET headline = '".$headline."',description = '".$description."' WHERE id = '".$newsId."'";

			$result = mysqli_query($connection, $query);
			if($result){
				$response['newsId'] = $newsId;
				$response['status'] = true; 
				$response['responseCode'] = 0; //News Updated Successfully
				$response['message'] = "News Updated Successfully";				
			}else{
				$response['status'] = false; 
				$response['responseCode'] = 105; //News not updated
				$response['message'] = "News Not Updated";
			}

		}

		if($request->{'action'} == 'DELETE_NEWS'){
			$isValidRequest = true;

			$userId = $request -> {'userId'};
			$newsId = $request -> {'newsId'};

			$query = "DELETE FROM news WHERE id = '".$newsId."'";

			$result = mysqli_query($connection, $query);
			if($result){
				$response['newsId'] = $newsId;
				$response['status'] = true; 
				$response['responseCode'] = 0; //News Updated Successfully
				$response['message'] = "News Deleted Successfully";				
			}else{
				$response['status'] = false; 
				$response['responseCode'] = 106; //News not updated
				$response['message'] = "News Not Deleted";
			}
		}

		if(!$isValidRequest){
			$response['status'] = false; 
			$response['responseCode'] = 100; //Invalid request action
			$response['message'] = "Invalid request action";
		}
	}else{
		$response['status'] = false; 
		$response['responseCode'] = 100; //Request action not defined
		$response['message'] = "Request action not defined";
	}

	echo json_encode($response);
	
?>

What I have tried:

honestly, i had not tried anything because I don't have any idea about the error. I visited many answers on stackoverflow and code project also website to seek answer. but i didn't understand it.