XMLHttpRequest No 'Access-Control-Allow-Origin'

我正在尝试使用ionic 2和angular 2进行登录访问。每当我按下正确的细节，我得到这个错误

XMLHttpRequest cannot load http://adirzoari.16mb.com/newapi.php. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8100' is therefore not allowed access.'

我也在网站上看到了一些类似的问题，但仍然没有得到任何解决方案。

这是我的PHP登录文件

        <?php
    header("Access-Control-Allow-Origin: *");
    header("Content-Type: application/json; charset=UTF-8");
    $conn = new mysqli("mysql.hostinger.co.uk", "a", "1234", "appd");
        //http://stackoverflow.com/questions/18382740/cors-not-working-php
        if (isset($_SERVER['HTTP_ORIGIN'])) {
            header("Access-Control-Allow-Origin: {$_SERVER['HTTP_ORIGIN']}");
            header('Access-Control-Allow-Credentials: true');
            header('Access-Control-Max-Age: 86400');    // cache for 1 day
        }
        // Access-Control headers are received during OPTIONS requests
        if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']))
                header("Access-Control-Allow-Methods: GET, POST, OPTIONS");         
            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']))
                header("Access-Control-Allow-Headers:        {$_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}");
            exit(0);
        }

        //http://stackoverflow.com/questions/15485354/angular-http-post-to-php-and-undefined
        $postdata = file_get_contents("php://input");
        if (isset($postdata)) {
            $request = json_decode($postdata);
            $username = $request->username;
            $password = $request->password;
                    $data = array();
            if ($password != "" && $username != "") {
            //echo "Server returns: " . $username . "Password is :" . $password;
                /*$arr=array();
                $st="select * from subnews order by SubID desc limit 10";
                $qr=$conn->query($st);
                while($row=$qr->fetch_assoc()){
                    $arr[]=$row;
                }
                echo json_encode($arr);*/
                $sel="SELECT id FROM users WHERE username='$username' AND password='$password'";
                $result=$conn->query($sel);
                $numrow=$result->num_rows;
                if($numrow == 1){ 
                            include 'tokengenerate.php'; 
                            $token=generateRandomString();    
                            $update="update users set token='$token' where username='$username' AND password='$password'";    
                            $qr=$conn->query($update);
                            if($qr){
                               $sel="SELECT id FROM users WHERE username='$username' AND password='$password'";
                               $query=$conn->query($sel);
                               while($row=$query->fetch_assoc(){
                                     $data[]=array(
                                     "name"->$row['username'],
                                     "token"->$row['token']
                                   );
                               echo json_encode($data);
                               }
                               } 
                }
            }
            else {
                header('HTTP/1.1 401 Unauthorized', true, 401);
            }
        }
        else {
            echo "Not called properly with username parameter!";
        }
    ?>