let credentials = {username:user,password:pass};
  let headers = new Headers();
  console.log(headers);
  this.http.post(this.serverUrl+'login.php',JSON.stringify(credentials),{headers: headers})
  .map(response =>{  return response.json()})
  .subscribe(data => console.log(data))
  ,error => console.log("loading error: ");

$data = file_get_contents("php://input");
$data = json_decode($data, TRUE);