...
数据： {
    用户名：onlyID，
    credoff：credoff
}，
...
 

I'm working on an existing script at the moment which uses Ajax, something I've never worked with before. I have a variable set in my javascript file which gets its value from an input field on my page. I need to use Ajax to post this to my PHP page only I've no idea where to start,

Im not sure what code you would need to see, but My javascript/AJAX code is, the variable I need to pass is 'var credoff'

$(".getPoint").click(function () {
    var theid = $(this).attr("id");
    var onlyID = theid.split("_");
    var onlyID = onlyID[1];
    var credoff = parseInt($(this).children('input.credoff:hidden').val());

    $.ajax({
        url: 'do.php',
        type: 'POST',
        data: "userID=" + onlyID,
        success: function (data) {
            if (data != "success1" && data != "success5") {
                $("#" + theid).text(data);
            } else {

                $("#thediv_" + onlyID).fadeOut("slow");
                $('#creditsBalance').fadeOut("slow");
                newbalance = parseInt($('#creditsBalance').text());

Wouldit have to be in this format?

data: "userID=" + onlyID,
"credoff=" + credoff

...
data: {
    userId: onlyID,
    credoff: credoff
},
...