Serial number grid PHP

  <?php

$s=mysql_query("SELECT * FROM  bus_detail where source_point='$_SESSION[source_point]' && destination_point='$_SESSION[destination]'");
$counter = 0;
while($row=mysql_fetch_array($s))
{
?>    
 <tr>
<td><?php echo ++$counter; ?></td>
<td><?php echo $row['bus_name'];?> </td>    
<td><?php echo $row['bus_no'];?></td> 
</tr>
<?php }?>

reference:- https://stackoverflow.com/questions/20322869/how-to-create-serial-number