Description:
------------
manual/en/language.variables.external.php#54634

line:

$this = unserialize($_SESSION['vars_serialized']);

should contain "xvars_..." not "vars_..."

I suggest my simplest version of that script:
<?php
if(!Array_Key_Exists('xvars_serialized',$_SESSION)) { $_SESSION['xvars_serialized']=""; echo "tudy\n";}
if(!$_SESSION['xvars_serialized']) {
    // If data has just been recieved, it is saved in $this and the current URL is builded.
    foreach ($_GET as $key => $value) $pa[$key] = $value;
    foreach($_POST as $key => $value) $pa[$key] = $value;
    $pa['doc_url'] = 'http://' .$_SERVER['HTTP_HOST'] .$_SERVER['PHP_SELF'] .'?' .$_SERVER['argv'][0];

    // If no POST data is recieved, nothing more is to be done. If POST data is recieved it is serialized to session and the page is redirected to itself with GET data but without POST data.
    if($_POST) {
        $_SESSION['xvars_serialized'] = serialize($pa);
        header('Location: ' .$pa['doc_url']);
        exit();
    }
}

// Just after the above redirecting, GET and POST data is unserialized into the object.
else {
    $_POST = unserialize($_SESSION['xvars_serialized']);
    $_SESSION['xvars_serialized'] = "";
}
?>

Viktor