Post variable is set but shows undefined index error

Post variable is set but shows undefined index error

I want to select a row from MySQL database which there are multiple rows.
I've chosen radio button for selection and I've put id of that row in
radio button value.
The problem is the posted radio button is set and when I echo it as you
can see in the code it shows me the right id.
When I want to select from database with MySQL query it gives me and index
undefined error, the strange point is when I select a table that contains
just one row this code is working but when number of rows are more than
one I am not able to select the chosen row.
Table code:
<?
if($_SESSION["count"]!=0 || $_SESSION["count"]!="")
{
?>
<!-- begining of levels informations -->
<form name="form2" method="POST" dir="rtl" action=""
style="font-family:'B_yekan';">
<div align="center" width="900" >
<table class="styled-table" cellspacing="0" width="900" border="1">
<tr>
<th width="10" scope="col" ></th>
<th width="60" scope="col">level</th>
<th width="60" scope="col">date</th>
<th width="60" scope="col">time</th>
<th width="54" scope="col">price</th>
<th width="60" scope="col">mark</th>
</tr>
<?php
$id = array();
while($rows=mysql_fetch_array($result)){
$id[]=$rows['id'];
?>
<tr>
<td><input class="styled-input" type="hidden" name="id[]" id="id"
value= "<? echo $rows['id']; ?>" /></td>
<td><input class="styled-input" type="text" name="lev" id="lev"
value="<? echo $tbl_name; ?>" /></td>
<td><input class="styled-input" type="text" name="date[]" id="date"
value="<? if($rows['date']=="1"){echo "even";}else{echo "odd";}?>"
/></td>
<td><input class="styled-input" type="text" name="time[]" id="time"
value="<?if($rows['time']=="pm1"){ echo"16 - 17:30";}
elseif($rows['time']=="pm2"){ echo "17:45 - 19:15";}
elseif($rows['time']=="pm3"){echo "19:30 - 21";}?>" />
</td>
<td><input class="styled-input" type="text" name="price[]" id="price"
value= "<? echo $rows['price']; ?>" /></td>
<td><input class="styled-input" style="padding: 5px;width:20px"
type="radio" name="mark[]" id="mark" value="<? echo $rows['id']; ?>"
/></td>
</tr>
<?php
}//end of loop
?>
</table>
</div>
<input class="styled-button-8" type="Submit" value="firstchoose"
name="firstchoose" />
<?}//end of if check for count?>
</form>
Select code:
<!-- first choose level -->
<?php
// Check if button name "Submit" is active, do this
if(isset($_POST['firstchoose']) && $_POST['firstchoose'] ==
'firstchoose')
{
$tbl_name=$_POST['lev'];
for($i=0;$i<$_SESSION["count"];$i++)
{
$checked =mysql_real_escape_string($_REQUEST['mark'][$i]);
echo $checked;
$sql2="SELECT * FROM $tbl_name WHERE
`id`='".mysql_real_escape_string($checked)."' ";
$result2=mysql_query($sql2);
$data = mysql_fetch_assoc($result2);
$count2=mysql_num_rows($result2);
}
if(isset($result2)){
?>
<script language="javascript">alert('the level is selected
successfully.'); </script>
<?php
}
}
?>
<!-- end of first choose level -->