think i found another solution and want to share it:
the solution with the switch and the solution with ajax made me think about how to solve this easier. why not make the form on one page and hide the different parts. what waas before a button to submit the part is now a button to hide previous part and show next.
<script type="text/javascript">
window.addEvent('domready', function()
{
$$('.blau').set('text', 'Erkennen Sie die Heilpflanze?');
$('page_2').slide('hide');
$('page_3').slide('hide');
$('page_4').slide('hide');
$('page_5').slide('hide');
var togglePrefix = 'toggle_', boxPrefix = 'page_', emptyPrefix = '';
$$('.submit_box a').addEvent('click', function(e)
{
e.stop();
var id = $(this.get('id').replace(togglePrefix,emptyPrefix));
var id_new = parseInt($(this).get('id').replace(togglePrefix, emptyPrefix)) + 1;
var next = ('page_'+id_new);
var id_old = $(this.get('id').replace(togglePrefix,boxPrefix));
$(id_old).set('slide', {duration: 'long', transition: 'linear'});
$(id_old).slide('out');
$(next).slide('in');
if (next == 'page_1')
{
}
if (next == 'page_2')
{
}
if (next == 'page_3')
{
}
if (next == 'page_4')
{
$$('.blau').set('text', '....und die letzte ist?');
}
if (next == 'page_5')
{
$$('.blau').set('text', 'Nur noch ein paar Daten:');
}
});
});
</script>
the html:
<form id="gewinnspiel" name="gewinnspiel" method="post" action="<?=$_SERVER[PHP_SELF]; ?>">
<div id="page_1">
<div class="inhalt-gewinn">
<div class="gewinn_bild"></div>
<div class="gewinn_form">
<div class="input_box">
<div><input type="radio" name="frage1" value="Kamille" /><span>Kamille</span></div>
<div><input type="radio" name="frage1" value="Kaktus" /><span>Kaktus</span></div>
<div><input type="radio" name="frage1" value="Krokus" /><span>Krokus</span></div>
</div>
<div class="submit_box"><a id="toggle_1" class="frage">nächste Frage...</a></div>
</div>
<div class="gewinn_werbung"></div>
</div>
</div>
<div id="page_2">
<div class="inhalt-gewinn">
<div class="gewinn_bild"></div>
<div class="gewinn_form">
<div class="input_box">
<div><input type="radio" name="frage2" value="Ringelblume" /><span>Ringelblume</span></div>
<div><input type="radio" name="frage2" value="Rotklee" /><span>Rotklee</span></div>
<div><input type="radio" name="frage2" value="Ringelkraut" /><span>Ringelkraut</span></div>
</div>
<div class="submit_box"><a id="toggle_2" class="frage">nächste Frage...</a></div>
</div>
<div class="gewinn_werbung"></div>
</div>
</div>
<div id="page_3">
<div class="inhalt-gewinn">
<div class="gewinn_bild"></div>
<div class="gewinn_form">
<div class="input_box">
<div><input type="radio" name="frage3" value="Enzian" /><span>Enzian</span></div>
<div><input type="radio" name="frage3" value="Eisenkraut" /><span>Eisenkraut</span></div>
<div><input type="radio" name="frage3" value="Eiche" /><span>Eiche</span></div>
</div>
<div class="submit_box"><a id="toggle_3" class="frage">nächste Frage...</a></div>
</div>
<div class="gewinn_werbung"></div>
</div>
</div>
<div id="page_4">
<div class="inhalt-gewinn">
<div class="gewinn_bild"></div>
<div class="gewinn_form">
<div class="input_box">
<div><input type="radio" name="frage4" value="Wollblume" /><span>Wollblume</span></div>
<div><input type="radio" name="frage4" value="Tulpe" /><span>Tulpe</span></div>
<div><input type="radio" name="frage4" value="Rose" /><span>Rose</span></div>
</div>
<div class="submit_box"><a id="toggle_4" class="frage">nächste Frage...</a></div>
</div>
<div class="gewinn_werbung"></div>
</div>
</div>
<div id="page_5">
<div class="inhalt-gewinn">
<div class="gewinn_bild"></div>
<div class="gewinn_form">
<div class="input_box_ende">
<?php echo '<input name="date" type="hidden" value="', time(), '" />'; ?>
<div class="nosee">eMail:<input name="email" type="text" id="email" value="<?=$_POST['email']; ?>" size="30" /></div>
<div><span>Vorname:</span><input type="text" name="vorname" value="<?=$_POST['vorname']; ?>"/></div>
<div><span>Nachname:</span><input type="text" name="nachname" value="<?=$_POST['nachname']; ?>"/></div>
<div><span>Strasse:</span><input type="text" name="strasse" value="<?=$_POST['strasse']; ?>"/></div>
<div><span>Ort:</span><input type="text" name="ort" value="<?=$_POST['ort']; ?>"/></div>
<div><span>PLZ:</span><input type="text" name="plz" value="<?=$_POST['plz']; ?>"/></div>
<div><span>eMail:</span><input type="text" name="imehl" value="<?=$_POST['imehl']; ?>"/></div>
</div>
<div class="submit_box"><input id="submit" name="senden" type="submit" value="Senden" /></div>
</form>
</div>
</div>
</div>
all working ! thx for the inspiration!