无法获取用户'的用户名使用PHP SDK

我能够获取所有用户的详细信息，除了我在网站中需要的用户用户名（在CI框架中编码）。我希望我的网站与facebook完全集成。我使用过PHP SDK代码。下面我提供了完整的代码。请让我知道我是否可以使用用户的fb-id和FQL获得用户的用户名。

<div id="fb-root"></div>
<script type="text/javascript">
    var button;
    var userInfo;   
    window.fbAsyncInit = function() {
        FB.init({ appId: 'your app id', //change the appId to your appId
        status: true, 
        cookie: true,
        xfbml: true,
        oauth: true});
      // showLoader(true);
        function updateButton(response) {
             button       =   document.getElementById('fb-auth');
             userInfo     =   document.getElementById('user-info');
             if (response.authResponse) {
                 //user is already logged in and connected
                 FB.api('/me', function(info) {
                     login(response, info);
                     //alert(info.email);

                 });
                 button.onclick = function() {
                     FB.logout(function(response) {
                         logout(response);
                     });
                 };
             } else {
                 //user is not connected to your app or logged out
                 button.innerHTML = 'Login';
                 button.onclick = function() {
                     FB.login(function(response) {
                         if (response.authResponse) {
                             FB.api('/me', function(info) {
                                 login(response, info);
                             });       
                         }
                         else
                         {
                             //user cancelled login or did not grant authorization
                             showLoader(false);
                         }
                     }, {scope:'email,user_birthday,status_update,publish_stream,user_about_me'});      
                 }
             }
         }
         // run once with current status and whenever the status changes
         FB.getLoginStatus(updateButton);
         FB.Event.subscribe('auth.statusChange', updateButton); 
    };
    (function() {
        var e = document.createElement('script'); e.async = true;
        e.src = document.location.protocol 
        + '//connect.facebook.net/en_US/all.js';
        document.getElementById('fb-root').appendChild(e);
    }());   
    function login(response, info){
        if (response.authResponse) {
        var accessToken                                 =   response.authResponse.accessToken;      
        userInfo.innerHTML                              = '<img src="https://graph.facebook.com/' + info.id + '/picture">' + info.name;
        button.innerHTML                                = 'Logout';
        showLoader(false);
        document.getElementById('other').style.display = "block";
        }
    }    
    function logout(response){
        userInfo.innerHTML                             =   "";
        document.getElementById('debug').innerHTML     =   "";
        document.getElementById('other').style.display =   "none";
        showLoader(false);
    }
    //stream publish method
    function streamPublish(name, description, hrefTitle, hrefLink, userPrompt){
        showLoader(true);
        FB.ui(
        {
        method: 'stream.publish',
        message: '',
        attachment: {
            name: name,
            caption: '',
            description: (description),
            href: hrefLink
        },
        action_links: [
            { text: hrefTitle, href: hrefLink }
        ],
        user_prompt_message: userPrompt
        },
        function(response) {
        showLoader(false);
        });
    }
    function showStream(){
        FB.api('/me', function(response) {
        //console.log(response.id);
        streamPublish(response.name, 'I like the articles of muffin.my', 'hrefTitle', 'http://muffin.my', "Share muffin.my");
        });
    }
    function share(){
        showLoader(true);
        var share = {
        method: 'stream.share',
        u: 'http://muffin.my/'
        };
        FB.ui(share, function(response) { 
        showLoader(false);
        console.log(response); 
        });
    }
    function graphStreamPublish(){
        showLoader(true);
        FB.api('/me/feed', 'post', 
        { 
            message     : "I love muffin.my muffin muffin muffin",
            link        : 'http://muffin.my',
            picture     : 'http://muffin.my/iphone/lucky7_ios.jpg',
            name        : 'iOS Apps & Games',
            description : 'muffin muffin muffin muffin muffin muffin muffin muffin muffin muffin muffin muffin muffin '
        }, 
        function(response) {
        showLoader(false);
        if (!response || response.error) {
            alert('Error occured');
        } else {
            alert('Post ID: ' + response.id);
        }
        });
    }
    function fqlQuery(){
        showLoader(true);
        FB.api('/me', function(response) {
        showLoader(false);
        //http://developers.facebook.com/docs/reference/fql/user/
        var query       =  FB.Data.query('select name, profile_url, sex, pic_small from user where uid={0}', response.id);
        query.wait(function(rows) {
           document.getElementById('debug').innerHTML =  
             'FQL Information: '+  "<br />" + 
             'Your name: '      +  rows[0].name            
              + "<br />" +
             'Your Sex: '       +  (rows[0].sex!= undefined ? rows[0].sex : "")                            + "<br />" +
             'Your Profile: '   +  "<a href='" + rows[0].profile_url + "'>" + rows[0].profile_url + "</a>" + "<br />" +
             '<img src="'       +  rows[0].pic_small + '" alt="" />' + "<br />";
         });
        });
    }
    function setStatus(){
        showLoader(true);
        status1 = document.getElementById('status').value;
        FB.api(
          {
        method: 'status.set',
        status: status1
          },
          function(response) {
        if (response == 0){
            alert('Your facebook status not updated. Give Status Update Permission.');
        }
        else{
            alert('Your facebook status updated');
        }
        showLoader(false);
          }
        );
    }   
    function showLoader(status){
        if (status)
        document.getElementById('loader').style.display = 'block';
        else
        document.getElementById('loader').style.display = 'none';
    }   
</script>

<button id="fb-auth">Login</button>
<div id="loader" style="display:none">
    <img src="ajax-loader.gif" alt="loading" />
      </div>
      <br/>
      <div id="user-info"></div>
      <br/>
      <div id="debug"></div>
      <div id="other" style="display:none">
    <a href="#" onclick="showStream(); return false;">Publish Wall Post</a> |
    <a href="#" onclick="share(); return false;">Share With Your Friends</a> |
    <a href="#" onclick="graphStreamPublish(); return false;">Publish Stream Using Graph API</a> |
    <a href="#" onclick="fqlQuery(); return false;">FQL Query Example</a>
    <br/>
    <textarea id="status" cols="50" rows="5">hello muffin hello muffin</textarea>
    <br/>
    <a href="#" onclick="setStatus(); return false;">Status Set Using Legacy Api Call</a>
</div>