Correct way to read 'echo json_encode( )' from JQuery

You should set the mime type aswell, wich, according to this question is application/json. Then jQuery will understand the answer is a json element. To do it, you'd do the following:

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

In your UpdateEditAStudent.php before printing anything.

You don't have to add a header to the PHP file, just use this Jquery parseJSON function:

Keep this PHP code as it is:

$Stuff = 'Hello world';$Success = true;$Content = $Stuff;$Response = array('Success' => $Success, 'Content' => $Content);echo json_encode($Response);

And for the JS:

$.ajax({      type: "GET",    url: "../pgs/UpdateEditAStudent.php",    data: "FirstName="+ $('#student_first_name').val(),    success: function(data){        // Here is the tip        var data = $.parseJSON(data);        alert(data.Content);    }});

You need to define the correct dataType or provide the correct header, as Lumbendil described.

You can manually define the dataType to json, so your code would look like:

$.ajax({     type: "GET",      url: "../pgs/UpdateEditAStudent.php",    data: "FirstName="+ sFirstName ,     dataType: "json",   ...etc