PHP mysql查询代码在localhost上完美运行，但不提交到实时服务器上的数据库

The following code works perfectly on my localhost machine. I haven't changed any code, apart from the username and password of the database. I'm a relative newbie to PHP, but all I'm wanting to do is have the user selected radio button information stored in the database. Here is my php..

session_start();

    if(isset($_POST['submit'])){


$conn = mysql_connect($HOSTNAME, $USERNAME, $PASSWORD)or  die( 'Could not connect: ' . mysql_error());


//mysql_select_db($DATABASE_NAME);
mysql_select_db($DATABASE_NAME, $conn) or die('');

    if (isset($_SESSION['username'])){
        $username= $_SESSION['username'];
    } else{
        $username= "FAIL";

    }

    $informant="informant";
    $mobilitylist ="mobilitylist";
    $transferslist ="transferslist";
    $dressinglist ="dressinglist";
    $toiletlist ="toiletlist";
    $bladderlist ="bladderlist";
    $bowelslist ="bowelslist";
    $groominglist ="groominglist";
    $feedinglist ="feedinglist";
    $bathinglist ="bathinglist";
    $stairslist ="stairslist";


    mysql_query("INSERT INTO digitaladl2 ($informant, $mobilitylist, $transferslist, $dressinglist, $toiletlist, $bladderlist, $bowelslist, $groominglist, $feedinglist, $bathinglist, $stairslist, username) 
                    VALUES ('".$_POST['informant']."','".$_POST['mobilitylist']."','".$_POST['transferslist']."',
                    '".$_POST['dressinglist']."','".$_POST['toiletlist']."','".$_POST['bladderlist']."','".$_POST['bowelslist']."'
                    ,'".$_POST['groominglist']."','".$_POST['feedinglist']."','".$_POST['bathinglist']."','".$_POST['stairslist']."','".$username."')");

    }
            ?>

The html form is too long to paste all fields, so here is just the first two radio button selections.

    <h4> Specifiy the informant when the Barthal Index is done in the community </h4>
    <input type="radio" name="informant" value="Patient">Patient<br>
    <input type="radio" name="informant" value="Main Support Person">Main Support Person<br>
    <input type="radio" name="informant" value="Both">Both<br>
    <input type="radio" name="informant" value="Other">Other<br>

    <h4><p> Mobility </p></h4>
    <input type="radio" name="mobilitylist" class="0" value="Immobile" >0 Immobile<br>
    <input type="radio" name="mobilitylist" class="1" value="Wheelchair independant (including corners/doors)" >1 Wheelchair independant (including corners/doors)<br>
    <input type="radio" name="mobilitylist" class="2" value="Help of one untrained person, including supervision" >2 Help of one untrained person, including supervision<br>
    <input type="radio" name="mobilitylist" class="3" value="Independant (may use aid)" >3 Independant (may use aid) <br>

Once the form is submitted on the live server, nothing happens - no data is entered into the database. Yet runs perfectly on the localhost server. Thanks in advance, all help appreciated!