/**
 * Simple closure class; Erling Ellingsen, 2003.
 *
 * http://steike.com/PhpClosures
 */

class Closure {	
  var $code;	
  var $env;	
	
  function Closure($code, $env) {
    $this->code = $code;
    $this->env = $env;
  }

  function call($__args = NULL) {
    // $this will probably be clobbered by the next step, so grab our
    // code and environment now
    $__code = $this->code;
    $__env =& $this->env;

    // set up the scope we need
    // extract() doesn't do references, so we can't use that
    foreach(array_keys($__env) as $__key)
      $$__key =& $__env[$__key];

    return eval($__code);
  }

  function makeGrabber($s) {
    $zot = $seen = array();

    // basically, grab everything that looks like a variable reference.
    // noone gets hurt if we happen to grab too much.
    if(preg_match_all('/\$(\w+)/', $s, $m))
      foreach($m[1] as $var) 
        if(!$seen[$var]++)
          $zot[] = "'$var' => &\$$var";

    $grabber = join(', ', $zot);

    $escaped = preg_replace("/['\\\\]/", "\\$&", $s);

    $grabber = "return new Closure('$escaped', array($grabber));";
    return $grabber;
  }
}

function closure($s) {
  return Closure::makeGrabber($s);
}


function _test_closure($n) {
  return eval(closure('
    return $n++;
  '));
}

$a =& _test_closure(5);
$b =& _test_closure(10);

assert($a->call() == 5);
assert($b->call() == 10);
assert($a->call() == 6);