giup do em combobox trong PHP voi ?

<?php
ob_start();
include 'config.php';
mysql_query("SET NAMES 'UTF8'");
$_get=$_GET['id'];
?>
<?php
   $array=array(50);
   $sql="Select * from sanpham where idSP=$_get";
   $result=mysql_query($sql) or die(mysql_error());
   $row=mysql_fetch_array($result);
   static $k=0;
?>
<form name="f">
   <select name="chungloai" size="1" onchange="replace(this.options.selectedIndex)">
   <?php $sqlstr2=mysql_query("SELECT * FROM chungloai");
                                       static $i=0;

                                       while($row_2=mysql_fetch_array($sqlstr2))
                                    {
                                       $array[$i]=   $row_2['idCL'];
                                       $i=$i+1;
                                       echo "<option value=".$row_2['idCL']." ".($row_2['idCL']==$row['idCL']?'Selected':'').">".$row_2['TenCL']."</option>";
                                    }

                           ?>
</select>
<select name="loai" >

                        <?php $sqlstr3=mysql_query("SELECT * FROM loaisp WHERE idCL=".$row['idCL']);

                                       while($row_3=mysql_fetch_array($sqlstr3))
                                    {

                                       echo "<option value=".$row_3['idLoai']." ".($row_3['idLoai']==$row['idLoai']?'Selected':'').">".$row_3['TenLoai']."</option>";
                                    }

                           ?>

   </select>

   <script type="text/javascript">

      var len=document.f.chungloai.options.length;
      var sites=new Array(len);


      for(i=0;i<len;i++)
      {
         sites=new Array();
         var j=0;
         <?php

            $str=mysql_query("SELECT * FROM loaisp WHERE idCL=".$array[$k]);
            $k++;
             while($row_4=mysql_fetch_array($str))
            {?>
               sites[j]=new Option("<?php echo $row_4['TenLoai'];?>","<?php echo $row_4['idLoai'];?>");
               j=j+1;
            <?php
            }?>
      }
      var temp1=document.f.loai;
       function replace(x)
       {

      for (m=temp1.options.length-1;m>0;m--)

      temp1.options[m]=null;
      for(i=0;i<sites
.length;i++)
      {

      temp1.options= new Option(sites
.text,sites
.value);
      }
      temp1.options[0].selected=true;

      }

   </script>
</form>