Wenn ich dich richtig verstanden habe meinst du sowas ähnliches...
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<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Unbenanntes Dokument</title>
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window.onload = function() {
var myform = document.forms[0];
myform.onsubmit = function() {
myform.elements["foo"].value = prompt("Was willst haben?", "");
return true;
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<body>
<form action="___DEINE_PHP_DATEI___">
<input type="hidden" name="foo" value="" />
Check 1: <input type="checkbox" name="bar" value="Checkbox_1_klicked" /><br />
Check 2: <input type="checkbox" name="foobar" value="Checkbox_2_klicked" /><br />
<input type="submit" />
</form>
</body>
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