คือหนูทำแล้วพอคลิกเลือกทั้งหมดมันไม่ยอมเลือกให้ค่ะ

 <script language="JavaScript">
	function ClickCheckAll(vol)
	{
	
		var i=1;
		for(i=1;i<=document.frmMain.hdnCount.value;i++)
		{
			if(vol.checked == true)
			{
				eval("document.frmMain.Chk"+i+".checked=true");
			}
			else
			{
				eval("document.frmMain.Chk"+i+".checked=false");
			}
		}
	}
</script>
<?
if ($room <> "")
{
	include "connect.php";
                mysql_select_db($dbname,$m)or die("ไม่สามารถเชื่อมต่อกับฐานข้อมูลได้").mysql_error();
	mysql_query("SET NAMES UTF8")
	$sql="select * from fix_tea  WHERE id_teacher='$valid_user' and year_fix = '$fix_year'order by class_fix ASC";   
   	$result=mysql_query($sql,$m)or die("ไม่สามารถเชื่อมต่อกับฐานข้อมูลได้").mysql_error(); 
   while($rs=mysql_fetch_array(	$result)){ 
     $class_fix = $rs["class_fix"];
   
   	 		    $sql1="select * from room WHERE id_room='$class_fix' order by id_room ASC";   
   				$result1=mysql_query($sql1,$m)or die("ไม่สามารถเชื่อมต่อกับฐานข้อมูลได้").mysql_error(); 
				$rs1=mysql_fetch_array($result1); 
				$room1 = $rs1["room"];   
?>   
	<input type="radio" name="class" value="<?=$rs['class_fix']?>" <? if($room==$rs['class_fix']){ 
  echo " checked='checked'";}?> onclick="location.href='messages_tea.php?room='+this.value"><?=$rs1['room']?>

<?php } ?>       
	</font></td></tr>
    <tr>
     <td>  <input name="CheckAll" type="checkbox" id="CheckAll" value="Y" onClick="ClickCheckAll(this);"></td>
    <td ><font color="#000000" size="3"  face="Arial, Helvetica, sans-serif">ลำดับ</font></td>
	<td  ><font color="#000000" size="3"  face="Arial, Helvetica, sans-serif">รหัส</font></td>
    	<td><font color="#000000" size="3"  face="Arial, Helvetica, sans-serif">ชื่อ - นามสกุล</font></td>
        

    </tr>
    <?
	$num = 0;
		$sql="SELECT*FROM student WHERE room = '$room'";
			$result=mysql_query($sql,$m)or die("ไม่สามารถเชื่อมต่อกับฐานข้อมูลได้").mysql_error();
			while($rs=mysql_fetch_array($result))
			{
				
				$num = $num+1 ;
				?>
                <tr>
                	 <td><input type="checkbox" name="chk[]" id="chk<?=$i;?>" value="<?=$rs["id_student"];?>"></td>

                	<td><font color="#000000" size="3"  face="Arial, Helvetica, sans-serif"><?=$num?>.</font></td>
                	<td  ><font color="#000000" size="3"  face="Arial, Helvetica, sans-serif"><?=$rs[id_student]?></font></td>
                   
                    <td ><font color="#000000" size="3"  face="Arial, Helvetica, sans-serif"><a href="messages_tea2.php?CusID=<?=$rs["id_student"]?>"><?=$rs[title_name]?><?=$rs[name_stu]?>&nbsp;<?=$rs[lastname_stu]?></a></font></td>
                </tr>
                <?
				
			}
			}
	?>