两道标题和解答，求改进_PHP

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>