correct HTTP header for json file

For JSON:

header('Content-Type: application/json');

For JSON-P:

header('Content-Type: application/javascript');

_{As @EricCope mentioned, you probably might also want to append ; charset=utf-8 if you're outputting UTF-8 data.}

Look at things like the Apache Axis spec. They favor application/json.

application/json is favored but usually web browsers don't know what to do with those headers and screws it up. For stuff like jquery, I have seen text/html recommended. If you are having errors pop up (e.g. download dialog box) then try text/html

I recently had a very strange run in with this.

I had a form which used jQuery to do an AJAX lookup against a PHP script, and then return the response as JSON, formed using PHP's json_encode() function.

It was all working fine for a couple of months, then this morning it stopped working... It turns out the javascript couldn't parse the JSON correctly.

My original method used eval.

I.e.

var p = eval('(' + msg + ')');

But that gave me the error:

missing ] after element list

I then tried using

var p  = JSON.parse(msg);

Using the json2.js library from http://json.org. This also failed.

I checked my JSON was formatted correctly using an online tool - it was.

In the end I tried changing the header type I was setting in the PHP script which was being called by jQuery AJAX.

I changed it from application/json to text/plain

And both the eval() and the JSON.parse solutions immediately worked... Much to my relief as I was running out of ideas.

Very odd and still don't know quite why, but thought I'd post here in case someone runs into a similar issue, or anybody can provide an explanation.

1) JSON :

Response is Dynamically generated data, according to the Query Parameters passed in the URL.

For Eg : { "Name": "Foo", "Id": 1234, "Rank": 7 }

Answer : header('Content-Type: application/json');

2) JSON-P :

Response is JSON data, with a function call wrapped around it.

For Eg : functionCall({"Name": "Foo", "Id": 1234, "Rank": 7});

Answer : header('Content-Type: application/javascript');

Even we can do like below:

<?php
    header('Content-Type: text/javascript; charset=utf8');
    header('Access-Control-Allow-Origin: http://www.example.com/');
    header('Access-Control-Max-Age: 3628800');
    header('Access-Control-Allow-Methods: GET, POST, PUT, DELETE');

    $file='rss.xml';
    $arr = simplexml_load_file($file);//this creates an object from the xml file
    $json= '('.json_encode($arr).');'; //must wrap in parens and end with semicolon
    print_r($_GET['callback'].$json); //callback is prepended for json-p
?>