dikini.net

//a generator implemented with iterators
function generator($it=null, $cb=null) {
  static $itor;
  static $callback;

  if(!isset($itor)) ($itor = $it; $callback=$cb; }

  if($valid()) { $out = $callback($current); $next(); return $out; }

  //or if you are not sure about the type of the above callables ($valid, $next,..)
  if( call_user_func($valid) ) { 
    $out = call_user_func( $callback, $current); 
    call_user_func( $next ); 
    return $out; 
  }

  else throw( new some_exception );
}