不能无法获取JSON文件跨域

I generate a list of objects in a json file using PHP and then i used jQuery to get data from it

    $.ajax({
        url: url,
        method: "get",
        dataType: "json"
        }).done(function (data) {
                for(var i=0; i < data.length; i++){
                document.getElementById("id01").innerHTML = data[i].Kategorianimi;

    }
    }).fail(function () {
        document.getElementById("id01").innerHTML = "cant get json";
    })

});

It worked ok in localhost but when i give a external host link to the url, it not work. Is there anyone has same issue with me and could you guy show me how to fix it? thanks.

When i add a header like this, then my JSON data was error

<?php
require_once "../pdo/kategoriaPDO.php";
header('Access-Control-Allow-Origin: *’);

/**
 * Created by PhpStorm.
 * User: dinhthinh
 * Date: 27/11/16
 * Time: 14:07
 */
$katepdo = new KatePDO();
$json = str_replace("\u0000","",json_encode($katepdo->listaKaikkiKategoriat(), true));
echo stripcslashes($json);

You must add your host to server's Access-Control-Allow-Origin header, or just send Access-Control-Allow-Origin: * header from server

The error You might be getting is that

No Access-Control-Allow-Origin header is present on the requeswted resource. localhost:8080 is thus not allowed Access.

This happens because browsers send a preflight OPTIONS requested to the server to see if it has access before sending the actual request

For security reasons, browsers restrict cross-origin HTTP requests initiated from within scripts. For example, XMLHttpRequest and Fetch follow the same-origin policy. So, a web application using XMLHttpRequest or Fetch could only make HTTP requests to its own domain. To improve web applications, developers asked browser vendors to allow cross-domain requests.

You server must then allow this by specifying the Access-Control-Allow-Orgin for localhost

Or for testing purpose you can use the CORS plugin for Chrome extension and test you code. But anyways later you need to enable CORS from the server.