What is the proper way to open a jQuery $.ajax connection between two https sites?

Question

I have two sites:

1. https://a.site.com
2. https://b.site.com

Both sites are served by the same wildcard SSL certificate

Part of https://a.site.com/a.php:

$(document).ready(function() {
    var tURL = "https://b.site.com/b.php?i=1";

    $.ajax({
        type: "GET",
        url: tURL,
        async: false,
        contentType: "application/json",
        dataType: 'jsonp', // Notice! JSONP <-- P (lowercase)
        success:function(json){
            alert("Success");
        },
        error:function(){
            alert("Error");
        }  
    });
})

On https://b.site.com/b.php I have:

//A query that returns a single value
$u = array('id' => $valueFromSQLQuery);
header('Content-type: application/json');
echo json_encode($u);

//returns {"id":630115}  --  "id" is always the same, the number changes

When I run https://b.site.com/b.php I get {"id":630115} displayed in my browser as I'd expect.

When I run https://a.site.com/a.php I get SyntaxError: missing ; before statement Line 1 {"id":630116} with an arrow in firebug pointing to the : in {"id":630116}

What am I doing wrong? From what I read, jsonp is the right way to go about doing ajax requests across domains. Is this because of SSL or am I missing something?

UPDATE @DrLivingston's answer pointed me in the right direction. The end result was:

https://b.site/b.php changed to :

//A query that returns a single value
header('Content-type: application/json');
echo $_GET['callback'] . '(' . "{'id' : $valueFromSQLQuery}" . ')';

And https://a.site.com/a.php changed to

$(document).ready(function() {
    var tURL = "https://b.site.com/b.php?callback=callback&i=1";

Answer 1

Without seeing what is actually returned "returns something like" and actually returning are different. I'm assuming you are actually generating a JSON response NOT a JSONP response which needs to have the callback in it (i.e., code not just json data).

See this: Simple jQuery, PHP and JSONP example?