Dropdown เปลี่ยนตามหัวข้อที่เราเลือก โดยส่งลงฐานข้อมูลเป็นตัวอักษรไม่ใช่ตัวเลข(ทำตามแบบ http://www.thaicreate.com/community/dependant-listmenu-dropdownlist.html)

function ListProvince(SelectValue)
		{
			form1.d_pn.length = 0
			
			//*** Insert null Default Value ***//
			var myOption 
			form1.d_pn.options[form1.d_pn.length]
			
			<?
			$intRows = 0;
			$strSQL = "SELECT * FROM sp_pn ORDER BY id_pn ASC ";
			$objQuery = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");
			$intRows = 0;
			while($objResult = mysql_fetch_array($objQuery))
			{
			$intRows++;
			?>			
				x = <?=$intRows;?>;
				mySubList = new Array();
				strGroup = <?=$objResult["id_p"];?>;
				strValue = "<?=$objResult["PN"];?>";
				strItem = "<?=$objResult["PN"];?>";
				mySubList[x,0] = strItem;
				mySubList[x,1] = strGroup;
				mySubList[x,2] = strValue;
				if (mySubList[x,1] == SelectValue){
					var myOption = new Option(mySubList[x,0], mySubList[x,2])  
					form1.d_pn.options[form1.d_pn.length]= myOption					
				}
			<?
			}
			?>																	
		}
		//**** List Province (End) ***//

</select>
           <select name="pro_n" id="pro_n" onChange = "ListProvince(this.value)">
                <option selected value="">&lt;--Please Select Team--&gt;-</option>
        <?
	$strSQL = "SELECT * FROM sp_product  ORDER BY id_p ASC ";
	$objQuery = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");
	while($objResult = mysql_fetch_array($objQuery))
	{
	?>
        <option value="<?=$objResult["id_p"];?>">
        <?=$objResult["PName"];?>
        </option>
        <?
	}
	?>
      </select>