<?php
header('Content-type: text/html; charset=windows-1251');
 $q=$_GET['q'];
 $searchterm=mysql_real_escape_string($q);
$searchtype=$_GET['searchtype'];
 
$mysqli=mysqli_connect('подключение к базе') or die("Database Error");
$sql="SELECT DISTINCT (".$searchtype.")
FROM DOC
WHERE ".$searchtype." LIKE '%".$searchterm."%' ORDER BY ".$searchtype."";
 
 $result = mysqli_query($mysqli,$sql) or die(mysqli_error());
 
 if($result)
 {
  while($row=mysqli_fetch_array($result))
  {
    echo $row['$searchtype']."\n";
  }
 }
?>