multiple select problem

[vidz]

In my edit user form I have multiple select area. In here i wanna show currently assigned laboratories for users and also provide access to edit them. This is how i have done it.

<?php 

$result1 = mysql_query("Select * 
                            from members 
                            JOIN lab_employee on members.emp_id = lab_employee.emp_id 
                            JOIN lab on lab_employee.lab_id = lab.lab_id 
                            where members.emp_id=$emp_id") 
               or die(mysql_error()); 
         $query="SELECT * FROM lab"; 
        $dropdown = "<select name='labid[]' multiple='multiple'  style='height:80px;' size='5'>"; 
        //$dropdown .= "<option value=''>Select lab to assign </option>"; 
        $result2 = mysql_query ($query); 
        while($row2 = mysql_fetch_assoc($result2))  

        { 

  $dropdown .= "\r\n<option value='{$row2['lab_id']}'"; 
            while($row1 = mysql_fetch_assoc($result1))  

              { 
                 if(($row1['lab_id'])==($row2['lab_id'])) 
                  { 
                      $dropdown .=" selected='selected'"; 
                  } 
             } 
  $dropdown .= ">{$row2['l_name']}</option>"; 
        } 
        $dropdown .= "\r\n</select>"; 
        echo $dropdown; 
       ?> 

But the problem is if there are multiple selections only 1st selection is shown. If there is only 1 selection then its ok. Need ur help to find the error