一個比較簡單的問題，請給以解決

Question

<script>
var onecount;
<?php 
    $i=1;
    for($i=1;$row=mysql_fetch_array($result);$i++)
    {
        echo 'subcat[$i]= new Array("$row[城市字段名]","$row[省代号]","$row[城市代号]");\n';
    }
    echo "onecount=$i;";
?>
subcat = new Array();
subcat[0] = new Array("杭州","1","1");
subcat[1] = new Array("丽水","1","2");
subcat[2] = new Array("金华","1","3");
subcat[3] = new Array("西安","2","4");
subcat[4] = new Array("宝鸡","2","5");
subcat[5] = new Array("延安","2","6");
subcat[6] = new Array("安康","2","7");
subcat[7] = new Array("汉中","2","8");
onecount=8;function changelocation(locationid)
    {
    document.myform.Nclassid.length = 0;     var locationid=locationid;
    var i;
    for (i=0;i < onecount; i++)
        {
            if (subcat[i][1] == locationid)
            { 
                document.myform.Nclassid.options[document.myform.Nclassid.length] = new Option(subcat[i][0], subcat[i][2]);
            }        
        }
        
    }    
</script><form method="POST" name="myform" >
<select name="classid" onChange="changelocation(this.value)" size="1">
      <option selected value="1">浙江</option>
      <option selected value="2">陕西</option>
 </select> 
    
    <select name="Nclassid">                  
        <option selected value="">==请选市==</option>
    </select>
</form> 
 
请参考一下上面的例子吧