สาบถามเกี่ยวกับ checkbox array ครับ บันทึกค่าแล้วแต่ใน database ไม่ตรงแถวที่เรากดบันทึก งง..แก้ยังไงดีครับ

<tr bgcolor=""> 
 <td width="2%" align="center"><input type="text" name="t6id[]" size="2" value="1" maxlength="2"  readonly style="width:100%;text-align: center;border:0px solid #B5B5B5;background: #dfdfdf;height:22px;"  OnKeyPress="return chkNumber(this)"/></td>
 <td width="8%" align="center"><input type="text" name="startdate[]" class="startdate"  value="<?php echo $rowt1["t6_date"];?>"placeholder="mm/dd/yyyy" style="width:100%;text-align: left;border:0px solid #c1c1c1;background: #dfdfdf;"></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co1" NAME="co1[]" value="1" <? if($rowt1['t6_1']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co2" NAME="co2[]" value="1" <? if($rowt1['t6_2']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co3" NAME="co3[]" value="1" <? if($rowt1['t6_3']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co4" NAME="co4[]" value="1" <? if($rowt1['t6_4']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co5" NAME="co5[]" value="1" <? if($rowt1['t6_5']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co6" NAME="co6[]" value="1" <? if($rowt1['t6_6']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co7" NAME="co7[]" value="1" <? if($rowt1['t6_7']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co8" NAME="co8[]" value="1" <? if($rowt1['t6_8']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co9" NAME="co9[]" value="1" <? if($rowt1['t6_9']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co10" NAME="co10[]" value="1" <? if($rowt1['t6_10']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co11" NAME="co11[]" value="1" <? if($rowt1['t6_11']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co12" NAME="co12[]" value="1" <? if($rowt1['t6_12']=="1"){ echo "checked"; }?>/></td>
 <td width="8%" align="center" bgcolor="#dfdfdf"><INPUT TYPE="checkbox" id="co13" NAME="co13[]" value="1" <? if($rowt1['t6_13']=="1"){ echo "checked"; }?>/></td>
 </tr>

$ti_id = array("1","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","21","22","23","24");
for($x=0;$x<count($_POST["t6id"]);$x++)
{

$ti_id6 = $ti_id[$x];
$t6id = $_POST["t6id"][$x];
$startdate = $_POST["startdate"][$x];
$co1 = $_POST["co1"][$x];
$co2 = $_POST["co2"][$x];
$co3 = $_POST["co3"][$x];
$co4 = $_POST["co4"][$x];
$co5 = $_POST["co5"][$x];
$co6 = $_POST["co6"][$x];
$co7 = $_POST["co7"][$x];
$co8 = $_POST["co8"][$x];
$co9 = $_POST["co9"][$x];
$co10 = $_POST["co10"][$x];
$co11 = $_POST["co11"][$x];
$co12 = $_POST["co12"][$x];
$co13 = $_POST["co13"][$x];

$sqlIn6 ="INSERT INTO t6(ti_id,Id,t6_date,t6_1,t6_2,t6_3,t6_4,t6_5,t6_6,t6_7,t6_8,t6_9,t6_10,t6_11,t6_12,t6_13)
			 		VALUES('$ti_id6','$MARK_ID1','$startdate','$co1','$co2','$co3','$co4','$co5','$co6','$co7','$co8','$co9','$co10','$co11','$co12','$co13')";

 $query  = mysql_query ($sqlIn6)  or die (mysql_error()); 

}