php ช่วยหน่อยครับ เลือกหัวข้อเรื่องในหน้า 1 พอเลือกหัวข้อเรื่อง ก็ให้โชว์ เนื้อหาในหน้า2

<?php
       

        $serverName = "localhost";
        $userName = "root";
        $userPassword = "123456";
        $dbName = "sqltemple";
        $con = mysqli_connect($serverName,$userName,$userPassword,$dbName);
        mysqli_set_charset($con, "utf8");

        $query = "SELECT * FROM tb_teach ";
        $result = mysqli_query($con,$query);
        $i =1;

    ?>
    <form name="f2" method="POST" action="">  
	<p><div id="content1">

    <center><h1>คำคม คำสอน</h1></center>

    <table id="table" width="800">
    	<tr>
        	<th width="50">เรื่องที่</th>
            <th>เรื่อง</th>
        </tr>

    <?php
        while($data = mysqli_fetch_array($result)) 
        {
    ?>        
        <tr>
        	<td> <?php echo $i;?> </td>
            <td> <a href="doctrines_2.php?id_teach=<?php echo $data["id_teach"];?>"> 
            <?php echo $data["title_teach"];?> </a> </td>
            <?php $i++;?> 
        </tr>
    <?php
        }
    ?>
    </table><br />
    </div>
	</div>
    </form>
    <?php 
        mysqli_close($con);  
    ?>
</body>
</html>

<?php

		$id_teach = null;
        if(isset($_POST["id_teach"]))
        {
            $id_teach = $_POST["id_teach"];
        }

        $serverName = "localhost";
        $userName = "root";
        $userPassword = "123456";
        $dbName = "sqltemple";
        $con = mysqli_connect($serverName,$userName,$userPassword,$dbName);
        mysqli_set_charset($con, "utf8");

        $query = "SELECT * FROM tb_teach WHERE id_teach ='".$id_teach."' ";
        $result = mysqli_query($con,$query);
        $data = mysqli_fetch_array($result); 
    ?>

    <form name="f2" method="POST" action=""> 
	<p><div id="content1"> <br>


   	  <table id="table" width=800>


        	<tr>
            	<th width=20>เรื่อง</th>
                <th> <?php echo $data["id_teach"];?> </th>
            </tr>

        </table>
        <table id="table" width=800>
   
        	<tr>
            	<td> <?php echo $data["content_teach"];?> </td>
            </tr>

        </table><br>

        
    </div>
	</div>
	</form>
	<?php
		mysqli_close($con);
	?>
</body>
</html>