basit bir örnek yazım daha iyi anlaman için
<select size="1" name="arama_bolgesi" class="languageselect" onChange="javascript: jumpLanguage(this);" style="font-family: Tahoma; font-size: 8pt; float: left; height: 22; width:90%">
<?php

$il_goster = mysql_query ("SELECT * FROM ilerimiz ");

 echo " <option value=\"\" selected>Lütfen Seçiniz...</option>";

  while ($il = mysql_fetch_array ($il_goster)) {

    echo "<option value=\"".$il['id']."\">=>".$il['iller']."</option>";
  }
//-------------------------------------------------------
?>
</select><br />
<select size="1" name="arama_bolgesi" class="languageselect" onChange="javascript: jumpLanguage(this);" style="font-family: Tahoma; font-size: 8pt; float: left; height: 22; width:90%">
<?php


 $ilce_goster = mysql_query ("SELECT * FROM ilceleri WHERE il_id='".$il['id']."' ");

 echo " <option value=\"\" selected>Lütfen Seçiniz...</option>";

  while ($ilce = mysql_fetch_array ($ilce_goster)) {

    echo "<option value=\"".$ilce['id']."\">=>".$ilce['iller']."</option>";
  }
?>

</select><br />