Error "trying to get property of non-object" when using ipinfo.io

I'm relatively new to PHP and I started messing with a site. And I found the following code that was giving error:

<?php        
 function ip_details() {
  $json = file_get_contents("http://ipinfo.io/");
  $details = json_decode($json);
  return $details;
 }
 $details = ip_details();
 $ip = $details->ip;//34    
 $local = $details->city;  //35
?>

This is the error that appears to me:

  

A PHP error was encountered   Severilty: Notice   Message: trying to get property of non-object   Filename: views / login_view.php   Line Number: 34

I know something about PHP but I did not understand what I was looking for here, but I did not find anything that would make me understand what that code was.

Does anyone notice this code that I can explain?