<script type="text/javascript">
function show() 
{
   document.pub.action = "pub.php"
   document.pub.method= "POST"
   document.pub.target= "_self"
   document.pub.act.value= "show"
   document.pub.submit();
}

<input type="button" value="Параметры" onclick="show();">

if($act=="show") {