jQuery to check if checkbox is checked on button click, then do multiple AJAX requests to PHP

Hi, I was wondering if it was possible to write some jQuery to check if on a button click, check if a certain checkbox is checked, and carry out an AJAX request to a PHP file.

The response if successful should post the JSON values to the "results" and "results2" div on my main html page.

I have tried the following code below

<form action="PHP.php" id="test" method="post">

<input type="checkbox" name="check1" value="1"/>one<br />
<input type="checkbox" name="check2" value="2"/>two<br />
<input type="checkbox" name="check3" value="3"/>three<br />

<input type="submit" id="submit_button" name="sub" value="Show"/>

</form>
        <script>

        $('#submit_button').click(function(){   
        event.preventDefault();         
            if ($('.check1').is(':checked')) {

            $.ajax({
                url: 'PHP.php',
                type: 'POST',
                data: json,
                success: function(data){

                    $("#results").empty();
                    $("#results").append(data); 


                    console.log(data);
                }

            });

            }

            if ($('.check2').is(':checked')) {

            $.ajax({
                url: 'PHP2.php',
                type: 'POST',
                data: json,
                success: function(data){

                    $("#results2").empty();
                    $("#results2").append(data); 


                    console.log(data);
                }

            });

            }

        });

        </script>

</div>

<div id="results">
</div>

<div id="results2">
</div>

Note: the PHP.php and PHP2.php file which I am loading I am only echoing JSON at the moment, until I can get this working, but the console is not logging any data at all.

I am having a bit of trouble in getting this to work. I was hoping for some help, or some guidance on the best way to do this?

Thanks in advance.