in your login script just add
PHP Code:
<?php
 $_SESSION['login'] = true;
then
PHP Code:
if ($_SESSION['login'] == true){
echo '<html><form action="upload.php" method="post" enctype="multipart/form-data"><br /><input type="file" name="info" /><br /><br /><input type="submit" value="Subir" /></form></html>';
}