Images not appearing in chess board - PHP

Our task is to create an 8x8 chess board wherein you have to put 8 queens in the board in which the queens won't be able to eat each other. My problem in this code is that the queen images (qb.png & qw.png) are not appearing in the output. Can someone point out what's wrong? Thank you very much.

<HTML> 
<head> 
    <title>Queen's Puzzle</title>
</head>

<style type = "text/css">
    table{
        border-collapse: collapse;
        width: 800px;
        border: 1px solid;
    }

    td{
        height: 100px;
        width: 100px;
    }

    .white{
        background-color: #FFFFFF;
    }

    .black{
        background-color: #000000;
    }

    .qw{
        width: 95px;
        height: 95px;
    }
</style>

<body> 
  <?php
  $pos = array(2, 7, 3, 6, 0, 5, 1, 4);
  $a = false;
  echo '<table>';
  for ($row = 0; $row < 8; $row++){
    echo '<tr>'; 

    for ($col = 0; $col < 8; $col++){
        if ($pos[$row] == $col){
            if($a){
                echo '<td img class="qw" src="qb.png"></td>';
                $a = false;
            } else {
                echo '<td img class="qb" src="qw.png"></td>';
                $a = true;
            }
        } else {
            if($a){
                echo '<td class="black"></td>';
                $a = false;
            } else{
                echo '<td></td>';
                $a = true;
            }
        }
    }
    echo '</tr>';
    $a = !($a);
}
echo '</table>';

      ?>
</body>
</html>

Solution

this:

echo '<td img class="qw" src="qb.png"></td>';

Should be:

echo '<td><img class="qw" src="qb.png"></td>';