a Form is as follow:
<form method="POST" action="accept_form.php">
<input name="demo1" type="text" value="">
<input type="submit" name="submit" value="go">
</form>

In the server, accept_form.php is as follow:
....
<script language="PHP">
  if(empty($demo1)
   {
             echo "demo1 is empty";
   }
</script>
....

Although I entered something is "demo1", empty() always returns true, and isset() works properly. what  is the problem? thank you.