Successfully passing json_encode'd variables from PHP to external .js file?

Question

First off let me say, I've never used JSON or AJAX before, but I think I understand the concept at least.

I'm only trying to pass some PHP values to a jquery function (located in an external .js file). I've tried everything I can possibly think of, and don't know what's going wrong here.

In index.php I have:

<?php
$data = array(1 => 'thisor', 2 => 'thatttt');
echo json_encode($data);
?>

..which obviously isn't the real data I'm wanting to pass, but it's just for testing. In my .js file I have the function:

  $.getJSON("index.php", function(data){
     alert('data loaded' + data);
  })
  .error(function() { alert("error"); });

and every time, it's throwing the error. However I've noticed if I use $.post with the same exact code following it, it doesn't throw an error anymore, and returns the data.

Also, is it necessary to 'echo' the json_encode? What if I don't want this information displayed on my webpage? Or.. I'm misunderstanding something here possibly.

Also x2, if it's worth noting, I read about 'header('Content-type: application/json');' that may need to go into the PHP file.. however when I did that, it no longer rendered the webpage in the browser, and instead just output the contents in plain text. Am I needing to do this somewhere else / make another external PHP file?

Apologies for any ridiculous questions, it really is my first day trying to learn this thing.

You could use $.post and use JSON.parse(data) to get the json object. Also I would suggest separating the php and the html into different files. So you could have something like getJson.php that sends the json and your index.php that just contains html with the javascript to send the request. — icanc
– icanc, Commented Mar 7, 2013 at 0:22
The only thing printed should be the JSON data. You should not mix it up with your main page's contents (how would getJSON() know then what to read?). — kapa
– kapa, Commented Mar 7, 2013 at 0:25
Yes, you need to echo json_encode(...). When you use AJAX, the output of the script is read by the AJAX callback function, it's not displayed on the webpage (unless the callback function displays it). — Barmar
– Barmar, Commented Mar 7, 2013 at 0:38

Captain Payalytic · Accepted Answer · 2013-03-07 00:55:51Z

1

It works fine for me. Are you sure that the ONLY thing output is the jon string? Is there anything else at all in the index.php file?

When using $.post, try changing your alert to:

 alert('data loaded(' + JSON.stringify(data)+')');

and check that all you see is the json string.

Since you've said that the index.php file is also outputting other stuff, here is an example of what you COULD do (I'm not saying that this is good practice). So you could write your index.php file similar to this:

<?php
if(isset($_GET['ajax'])) {
  $data = array(1 => 'thisor', 2 => 'thatttt');
  echo json_encode($data);
  exit;
  }
?>
<script type="text/javascript" src="http://code.jquery.com/jquery-1.9.1.min.js">
</script>
<script type="text/javascript">
<!--
$.post("index.php?ajax", function(data){
     alert('data loaded(' + JSON.stringify(data)+')');
  })
  .error(function() { alert("error"); });
// -->
</script>

edited Mar 7, 2013 at 0:55

answered Mar 7, 2013 at 0:40

Captain Payalytic

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2 Comments

Heather Wilson Over a year ago

No it's not.. I think I've misunderstood exactly how this is done. It outputs all the data on the page. Edit: How does one conventionally go about doing this? If I have a page 'index.php' and I need to manipulate the variables in it using jQuery.. I need another .php file in which to do json_encode()? Very confused.

Captain Payalytic Over a year ago

You can either call another php file OR you can code the index.php file so that, on receipt of the ajax request (maybe use a query string to indicate that it's an ajax request), it outputs JUST the json string and then immediately exits.

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