if (isset($_SESSION['name'])){
    //select BID and duedates which are between the range of 1-3 days
    //  before due date from current date   
    $query = "SELECT DueDate FROM item WHERE DueDate BETWEEN '$warning2' and '$warning' and user='$_SESSION[name]' ORDER BY DueDate DESC";
    $find = mysql_query($query);    
    $alert = mysql_num_rows($find);
    if ($alert>=1){
        echo "You have got " .$alert. " item(s) due on: </br >";
        while ($item = mysql_fetch_array($find)){
             echo $item['DueDate'];         
             echo "<br />";
        }
    }
    echo "Success!";
}

Question: How do i input all this code into a single php variable, say $alert. I am not clear of where to put single quotes or double quotes to make it work. At the end of the day, I will be using the variable for a javascript alert box.