<?php
if (empty($_SESSION)) {
header("Location: http://mydomain.com/myOtherPageForNoLoginUser.php");
die();
}
?>
<?php if (empty($_SESSION)) header("Location: http://mydomain.com/myOtherPageForNoLoginUser.php");
die();
else
header("Location: http://mydomain.com/myOtherPageForLoginUser.php");
die();
?>
<?php if (isset($_SESSION['название сессии'])) header("Location: http://mydomain.com/myOtherPageForLoginUser.php");
die();
else
header("Location: http://mydomain.com/myOtherPageForNoLoginUser.php");
die();
?>