formular funktioniert nicht

<form action="index.php?link=guestbook_eintragen_eintrag_text.php" method="post">



        name:


        <input name="name" size="">


        




        topic:


        <input name="title" size="">


        




        message:
        <textarea name="text" cols="50" rows="10"></textarea>


        




        e-mail:


        <input name="mail" size="">


        




        homepage:


        <input name="hp" size="" value="http://">


        




        <input type="submit" value="insert">
    </form>

<?php


$name=$_GET['name'];
$title=$_GET['title'];
$datum=$_GET['datum'];
$text=$_GET['text'];
$hp=$_GET['hp'];
$mail=$_GET['mail'];


echo ''.$name.'
';
echo ''.$title.'
';
echo ''.$datum.'
';
echo ''.$text.'
';
echo ''.$hp.'
';
echo ''.$mail.'
';


		if (isset($_GET[topic]) && in_array($_GET[topic], $inc_array) ) {
        include("./includes/".$_GET[topic].".php");
        } else {
        include('./includes/config.php');
        }


echo '<center>[b]Insert entry[/b]</center>';


$timestamp = time();
$datum = date('m.d.y');


$write = "INSERT INTO `usa_guestbook` ( `name`, `topic`, `date`, `text`, `webpage`, `email`, `id` )
                VALUES ( '$name', '$title', '$datum', '$text', '$hp', '$mail', '' )";
                    $swrite = mysql_query ($write, $db_link);
                        if ($swrite) {
                        	echo '
<center>All OK!</center>
';


                        }
                        else {
                            echo "
 Fehler!_1 ";
                        };


?>