PHP Cacher variables dans URL

<form method="POST" action="monscript.php" name="tonform">
    <input type="hidden" value="tavariable" name="variable1">
    <a href="javascript:document.tonform.submit();">Ton lien</a>
</form>

<form method="POST" action="monscript.php" name="tonform">
    <input type="hidden" value="-" name="mdp" id="champmdp">
    <a href="javascript:document.tonform.submit();">Ton lien</a>
</form>

<script language="JavaScript">
<!--
if (document.getElementById) {
    document.getElementById("champmdp").value = passe;
} else if(document.all) {
    document.all["champmdp"].value = passe;
}
// -->
</script>