<%
  $a = 'value';

  function foo()
  {
    global $a;

    unset($a);
  }

  function bar()
  {
    global $a;

    $a = 0;
  }

  print "$a\n";
  print isset($a) . "\n";

  foo();
  print "$a\n";
  print isset($a) . "\n";

  bar();
  print "$a\n";
  print isset($a) . "\n";
%>