jQuery example for Accessing the Joomla Framework via an AJAX Call

gistfile1.txt

$.ajax({
    type: 'POST',
    url: '/path/to/PHP/file',
        dataType: 'json',
        data: { catid: $("#catid").val() },
        success: function(data){
            $('.item-page').prepend(
                $('<h2>').append(
                    $('<span>')
                        .addClass('subheading-category')
                        .text(data.msg)
                )
            )
        },
        error: function(XMLHttpRequest, textStatus, errorThrown) {
            console.log('There was an error.');
        }
});