PHP & JSON - Callback Function

Question

I'm a JS newbie ... I've got a PHP page w/ a JavaScript function which makes a JSON call to a database server. That JSON function returns an array, which I need to parse and do something with. I understand the need for the callback (currently getting the undefined errors), but am confused as to the actual syntax. Can anyone provide a bit of guidance?

Here's my JSON function in the PHP Page:

var GETDATA = function() 
  {
   $(document).ready(function()
   {
     $.getJSON('api.php', function(data) 
      {
     $.each(data, function(key, val) 
      {
        UpdateGraph(val.x, val.y, val.z);
      });
      });
   });
  };`

**The UpdateGraph function takes the variables and performs some further business logic

The api.php page connects to a database, grabs a recordset, and puts it into a JSON array. the last line of that is

echo json_encode($arr);

I understand the asym flow of this, and that I need a callback function to fire when the data is received ... but I'm lost in how to make this happen. Any guidance would be most appreciated.

That's a JavaScript function. Functions don't exist in JSON since it is a data exchange format. The overall code looks "ok" though you probably don't need to use a .ready callback. Is the function executed? What is the value of data? What are the undefined errors you get? — Felix Kling
– Felix Kling, Commented Jun 8, 2012 at 18:26
what triggers the call to the API? is it a click event? or on load? — solidau
– solidau, Commented Jun 8, 2012 at 18:27

Nicolás Torres · Accepted Answer · 2012-06-08 18:29:27Z

1

First of all, JSON is a format, not a language.

You already have the callback

$.getJSON('api.php', function(data)

function(data) is your callback, and data is your returned data from php, inside of it you should add your code or what you want to do with the data.

 $.each(data, function(key, val){
        UpdateGraph(val.x, val.y, val.z);
 });

$.each will cycle through your data array and call the UpdateGraph function

answered Jun 8, 2012 at 18:29

Nicolás Torres

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Comments

brasofilo · Accepted Answer · 2017-05-04 02:34:08Z

0

Your returned json object (data) should also have a key value relationship for each nested object inside "data". To put in a simple phrase...treat json object like a hash map with key/value

so say i have two object :object a and object b inside "data"

 $.each(data.a, function(key, val){
        UpdateGraph(val.x, val.y, val.z);
 });


 $.each(data.b, function(key, val){
        UpdateGraph(val.x, val.y, val.z);
 });

are valid

edited May 4, 2017 at 2:34

brasofilo

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answered Jun 9, 2012 at 8:35

Sayan

1

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