save facebook user details to database

I have a login to facebook button and all works well, on click i would like the users id, first and last name to be added to a database (i have a php file for this which works nicely) The problem i have is posting the data to the php file. My code is below an开发者_运维百科d i get the error $ is not defined. I understand that i will need to reference the jquery file. However i don't know where to as the script already references facebooks js file

<script src="http://connect.facebook.net/en_US/all.js"></script>

<script>
    FB.init({ 
        appId:'137558232981530', 
        cookie:true, 
        status:true, 
        xfbml:true 
    });

    FB.Event.subscribe('auth.login', function(response) 
    {

        FB.api('/me', function(response) {


        $.post("usersignup.php", { 
        facebookid: response.id, 
        email: response.email, 
        firstname: response.first_name, 
        lastname: response.last_name 
        });


});

    });
</script>

1.You have to reference jQuery above your script (anywhere above, reference order does not matter for independent scripts(that does not conflict with each other)) e.g.

<script src="http://connect.facebook.net/en_US/all.js"></script>
<script src="jquery.js"></script>

2.Try using jQuery.post instead of $.post as the '$' can conflict with other script APIs (like prototype). jQuery conflicts with other frameworks