Hocam elimde benzer bir session kontol ü var burdan bakarak düzenleme yapabilirsiniz.
<body>
<?php if (isset($_SESSION["oturum"])) {?>
<div id="header">
<div class="header">
<ul class="ust_sec">
<li class="arkadas"></li>
<li class="mesaj"></li>
<li class="bildirim"></li>
</ul>
</div>
</div>
<div class="alt">
<a href="cikis.php">Çıkış Yap</a>
Hoşgeldin, <?php echo $_SESSION["oturum"]; ?>
<form action="gonder.php" method="post">
<table>
<tr>
<td>Mesaj Gönderin</td>
</tr>
<tr>
<td>Kişi seçin</td>
<td>
<select name="kime" id="">
<?php
$sor = mysql_query("select * from uyeler");
while ($row = mysql_fetch_array($sor)) {
echo "<option value='".$row["id"]."'>".$row["kadi"]."</option>";
}
?>
</select>
</td>
</tr>
<tr>
<td>Mesajınız</td>
<td>
<textarea name="mesaj" id="" cols="30" rows="10"></textarea>
</td>
</tr>
<tr>
<td> </td>
<td>
<input type="submit" value="Gönder" name="gonder">
</td>
</tr>
</table>
</form>
</div>
<?php } else { ?>
<form action="giris.php" method="post" name="Form1">
<table>
<tr>
<td>Adınız</td>
<td><input type="text" name="adi"></td>
</tr>
<tr>
<td>Parola</td>
<td><input type="password" name="pw"></td>
</tr>
<tr>
<td> </td>
<td><input type="submit" value="Gönder"></td>
</tr>
</table>
</form>
<?php } ?>