nested if statements causing error

[ploppy]

hello. I seemed to have got lost with my if statements here and cannot see where to use elseif . I am getting the duplicate response message ok, but if I submit with blank input, it produces NaN error, which I know is JavaScript but I think it is because of the order of the if statements. If someone could help me with this I would be very grateful. Thanks.

 

if (!empty ($_POST['item']))
{
  $data = split(',',$_POST['item'][0]);
  $duplicates = array();

foreach ($data as $val)
{
if ( $val != "" )
{
  $sql = "SELECT custref FROM boxes WHERE custref='$val' Union SELECT item FROM act WHERE item='$val'";
  $qry = mysql_query($sql) or die(mysql_error());

  if(mysql_num_rows($qry))
  {
  $duplicates[] = $val;
  }
}
}

if(count($duplicates))
{
    $response_array['status'] = 'error';
    $response_array['message'] = 'No duplicate files';
}
}
//check the name field
elseif(empty($authorised)){

    //set the response
    $response_array['status'] = 'error';
    $response_array['message'] = 'Name cannot be blank';

//check the service field
}