Undefined index: error
<p>i am a beginner in php,i am facing a problem with the following code. it shows undefined index error."Undefined index: username in C:\wamp\www\phpmyadmin_practise\member.php on line 7
you must be login!".i can't understand what shoul i do.</p>

<p>

<pre><code>session_start();
if($_SESSION['username'])
{
echo "Welcome,".$_SESSION['username']."!&lt;br&gt; &lt;a href ='logout.php'&gt; Logout &lt;/a&gt; &lt;br&gt; &lt;a href='changepassword.php'&gt; changepassword &lt;/a&gt; &lt;br&gt;";
}
else
{
    die("you must be login!");
}
</code></pre>

<p>?></p>
