PHP注意:尝试获取非对象的属性

When I get file content from javascript, decode it and get the value of object. It display trying to get property of non-project. However, the object variable is successfully pass to another php class. May I know why it cause this problem? I had try all the solution from stackoverflow but it not work and it also display the same error. The following is my code:

$chat_info = file_get_contents("php://input");
$chat_request = json_decode($chat_info);
$username = $chat_request->username;
$messageContent = $chat_request->messageContent;
$dateTime = $chat_request->date_time;
$channel = $chat_request->channel;
$event = $chat_request->event;

You can also do this:

$chat_info = file_get_contents("php://input");
$chat_request = json_decode($chat_info,true);
$username = $chat_request['username'];
$messageContent = $chat_request['messageContent'];
$dateTime = $chat_request['date_time'];
$channel = $chat_request['channel'];
$event = $chat_request['event'];

And after it if it show any error like undefined index then the $chat_info variable does not contain the value of a key that you want.

Probably one of the object which you use get from time to time NULL value. Check this out, i hope that is correct answer.