AJAX concept help

JSON isn't absolutely required, its just a way of formatting data in such a way which can make it more human readable (see below).

If your AJAX is calling a php script which is to return data from a Database, php has built in functions to format the results in JSON.

That being said, you can just return a string back to PHP, it all depends on the circumstances your using AJAX in the first place.

Consider a JSON object for a customer and perhaps some information about previous orders. JSON is useful when returning data back from an SQL query back to a php script

{  
   "Client Details":{  
      "Client name":"Chris Jones",
      "DOB":"23/07/1984",
      "Address":{  
         "Address Line1":"Our House",
         "Address Line2":"In the middle of our street",
         "Post/ZIP code":"PO19 9KK"
      },
      "Products ordered":{  
         "Computer hardware":{  
            "Processor":"Intel I7",
            "Memory":"32GB"
         },
         "Computer Software":{  
            "Operating System":"The one thats free",
            "Office software":"Pen and Paper"
         }
      }
   }
}

The predecessor to the above is XML and using the same data as above, would look like this:

<?xml version="1.0" encoding="UTF-8" ?>
    <Client Details>
        <Client name>Chris Jones</Client name>
        <DOB>23/07/1984</DOB>
        <Address>
            <Address Line1>Our House</Address Line1>
            <Address Line2>In the middle of our street</Address Line2>
            <Post/ZIP code>PO19 9KK</Post/ZIP code>
        </Address>
        <Products ordered>
            <Computer hardware>
                <Processor>Intel I7</Processor>
                <Memory>32GB</Memory>
            </Computer hardware>
            <Computer Software>
                <Operating System>The one thats free</Operating System>
                <Office software>Pen and Paper</Office software>
            </Computer Software>
        </Products ordered>
    </Client Details>

I'm sure you'd agree that JSON is much more friendly/easier to read

Hi nicholas maddren

JSON is really just a bunch of text that's formatted in a way that's easy for a web browser to convert to JavaScript.

In your case, you might have a web page that makes an AJAX request to your web server. The request will point to a specific resource on your server: for example get_data.php. This would just be a PHP page that you create and program. You would program it to return the JSON-formatted data. After the web page sends the request to this page (get_data.php for example), it waits until the server sends back the data. Your php file needs to be programmed to send a text response back.

The php file doesn't have to send JSON. It can send XML as Chris Jones points out. But the php file might just send a sentence or a single word like "submitted." It's up to you to figure out what kind of information you want to receive back from the server and place into the web page. I hope that helps.

The most common use of JSON is something you get from an API like Flickr or Twitter or even Treehouse. In fact all of the data about every badge you've earned on Treehouse is available as one JSON file. http://teamtreehouse.com/nicholasmaddren.json

Once you've got that then you can easily manipulate it like SQL. Something like, get me the date I earned my last badge, calculate how many badges I've earned, get the date I joined Treehouse. You can do all of this using JavaScript.

Another use of JSON is if you want to store more than a variable in local storage.