Tutorial til søgefunktion

Jeg har tidligere haft oprettet spørgsmål hvor jeg savner et færdigt script, men da jeg ikke kunne få det til at virke, må jeg nok gå den slagne gang og lære det... men hvis nogen vil, har jeg koden til det gamle liggende her!

søgesiden:
<form method="POST" action="?mainkategori=1&show=seek"  name="test">

<input type="hidden" name="action" value="seek">
<input type="hidden" name="mainkategori" value="<?=$mainkategori?>">

<table >
<tr>
        <td width="138" align="left"><span class="style2">Buy / Sell</span></td>
        <td width="162" align="left"><select name="userpost_sell" class="style2">
        <option value="">--Select--</option>
          <option value="1">Buy</option>
          <option value="2">Sell</option>
        </select></td>
    </tr>
    <tr>
        <td width="138" align="left"><span class="style2">Product Group:</span></td>
        <td width="162" align="left"><select name="userpost_group" class="style2" onChange="subgroup();">
        <option value="0">---- SELECT ----</option>
        <option value="1">Wood</option>
        <option value="2">Steel/Iron</option>
        <option value="3">Textiles</option>
        <option value="4">Food/Agriculture</option>
        <option value="5">Vehicles</option>
        <option value="6">Investment</option>
        </select></td>
    </tr>
   
    <tr>
        <td align="left"><span class="style2">Product Subgroup</span></td>
        <td align="left"><select name="userpost_sub" class="style2">
        <option value="0">---- SELECT ----</option>
       
        </select></td>
    </tr>
    <tr span class="style2">
      <td align="left">Country:</td>
      <td align="left"><span class="style2"><select name="land" class="style2">
        <option value="0">---- SELECT ----</option>
        <?
        $res = mysql_query("SELECT * FROM lande ORDER BY navn");
        while( $land = mysql_fetch_row($res) )
        {
            echo"<option value=\"$land[1]\">$land[1]</option>";
        }
        ?>
        </select></span></td>
  </tr>
    <tr class="style2">
      <td align="left">Search text:</td>
      <td align="left"><input name="searchtext" type="text" class="style2" size="30"></td>
  </tr>
    <tr>
            <td align="left"><input type="submit" name="submit" value=" Submit " class="style2"></td>
        <td></td>
    </tr>
    </table>
      </form>
-----------------------------------
"engine" :D

$query = 'SELECT * FROM userpost INNER JOIN brugere ON userpost.userpost_bruger = brugere.id';
            $sell = $_POST[userpost_sell];
            $userpost_group = $_POST[userpost_group];
            $userpost_sub = $_POST[userpost_sub];
            $land = $_POST[land];
            $searchtext = $_POST[searchtext];
           
    $conditions = array();
    if($sell) {
        $conditions[] = 'userpost_sell LIKE \'%".$sell."%\'';
    }
    if($userpost_group) {
        $conditions[] = 'userpost_group LIKE \'%".$userpost_group."%\'';
    }
    if($userpost_sub) {
        $conditions[] = 'userpost_sub LIKE \'%".$userpost_sub."%\'';
    }
    if($land) {
        $conditions[] = 'land LIKE \'%".$land."%\'';
    }
    if($searchtext) {
        $conditions[] = 'userpost_over LIKE \'%".$searchtext."%\' OR userpost_text LIKE \'%".$searchtext."%\'';
    }
   
    if(!empty($conditions)) {
        $query .= ' WHERE '.implode(' AND ', $conditions);
    }

    $foresp = mysql_query($query);

b