关于PHP网页用户登陆后显示注销.而登陆前则只显示注册登陆连接的有关问题

关于PHP网页用户登陆后显示注销.而登陆前则只显示注册登陆连接的问题
如题.我是用PHP的.
<div>
<ul>
<?php
session_start();
echo $_SESSION['username']; 
?>
<li>Login</li>
<li>Apply for user1</li>
<li>Apply for user2</li>
</ul>
</div>
------------以上是在index.php写的------------

我是想当登陆后.login , Apply for user1 , Apply for user2都不显示.只显示用户名和注销.
然后注销后就会显示回login , Apply for user1…….
求大神们教教我.

[解决办法]
请给出index.php完整代码.
[解决办法]

PHP code

<?phpsession_start();?><ul><?php if(!empty($_SESSION['username'])){?>    <li>用户名<?php echo $_SESSION['username'];?></li>    <li>注销</li><?php }else{?>    <li>Login</li>    <li>Apply for user1</li>    <li>Apply for user2</li><?php }?></ul>
[解决办法]
探讨


PHP code
<?php
session_start();
?>
<ul>
<?php if(!empty($_SESSION['username'])){?>
    <li>用户名<?php echo $_SESSION['username'];?></li>
    <li>注销</li>
<?php }else{?>
    <li>Login</li>
    <li>Apply……

[解决办法]
<?php
session_start();
?>
<ul>
<?php if(!empty($_SESSION['username'])){?>
   <li>用户名<?php echo $_SESSION['username'];?></li>
   <li>注销</li>
<?php }else{?>
   <li>Login</li>
   <li>Apply for user1</li>
   <li>Apply for user2</li>
<?php }?>
</ul>