从多个字段下拉菜单

This is an addition to the previous questions I asked. In my drop down box for engravers I would like the box to collect the surnames from three fields, Engraver1Surname, Engraver2Surname and Engraver3Surname. I also want each name only to appear once and to be in alphabetical order. My code doesn't work which means I've got it wrong again. This stuff is really challenging and I'm loving it but I don't want to be a serial pest.This is what I tried.

$sql = "SELECT DISTINCT Engraver1Surname, Engraver2Surname, Engraver3Surname FROM engravers Where Engraver1Surname, Engraver2Surname, Engraver3Surname <> '' AND  Engraver1Surname, Engraver2Surname, Engraver3Surname IS NOT NULL ORDER by Engraver1Surname, Engraver2Surname, Engraver3Surname";
    $result = mysql_query($sql);

    echo "<select name\\='Engraver1Surname'>";
      echo "<option value='$_POST'>Engraver</option>";
      while ($row = mysql_fetch_array($result)) {
      echo "<option value='" . $row['Engraver1Surname'] . "'>" .$row['Engraver1Surname'] . "</option>";
      }
      echo "</select>";

$name=array('Engraver1Surname','Engraver2Surname','Engraver3Surname');

$option=array();

while ($row = mysql_fetch_array($result)) {

      for($x=0;$x<3;$x++){
      $option.=$row[$name[$x]];
      }

}

asort($option);

for($y=0;$y<sizeof($option);$y++){
echo "<option value='" . $option[$y]. "'>" .$option[$y] . "</option>";
}

echo "</select>";

Hope it fix to your question