两道题目和解答，求改进

初学 php ，很多都不懂，能不能指导一下这两道题目更好的解法，谢谢
<html>
<body><table border="1" cellpadding="0" cellspacing="0">
        <tr>
                <td width=300>
                    a
                    <br />
                    <br />
                    <br />
                </td>
                <td width=300>
                    <br />
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                    b
                    <br />
                    <br />
                </td>
        </tr>        <tr>
                <td>
                    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                    c
                    <br />
                    <br />
                    <br />
                </td>                <td>
                    <br />
                    <br />
                    d
                </td>
        </tr>
</table>
</body>
</html><html>
<body>
    <?php
        for ($i=8; $i>=4; $i=$i-2) {
            for ($k=8-$i; $k>0; $k--) {
                echo "&nbsp;";
            }
            for ($j=$i; $j>0; $j--) {
                echo "*";
            }
            echo "<br>";
        }
            
            echo "&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;*";
    ?></body>
</html>