Yazılım | Programlama PHP mysql kodum çalışmıyor.

<?php
 
// get the HTTP method, path and body of the request
$method = $_SERVER['REQUEST_METHOD'];
$request = explode('/', trim($_SERVER['PATH_INFO']));
$input = json_decode(file_get_contents('php://input'),true);
 
// connect to the mysql database
$link = mysqli_connect('', '', '', 'remakenetwork');
mysqli_set_charset($link,'utf8');
 
// retrieve the table and key from the path
$key = array_shift($request);
 
 
// create SQL based on HTTP method
switch ($method) {
  case 'GET':
    $sql = "select * from `users`".($key?" WHERE username=$key":''); 
    break;
} 
 
// excecute SQL statement
$result = mysqli_query($link,$sql);
 
 
// print results, insert id or affected row count
if ($method == 'GET') {
  if (!$key) echo '[';
    echo json_encode(mysqli_fetch_object($result));
  if (!$key) echo ']';
} elseif ($method == 'POST') {
  echo mysqli_insert_id($link);
} else {
  echo mysqli_affected_rows($link);
}
 
// close mysql connection
mysqli_close($link);

[{"id":"1","username":"MargeSimpson","country":"Brazil","password":"MargeSimpson","created_at":null,"ip_address":null,"game_token":"MargeSimpson","city":null,"ban":"0"}]