devuelve el año y mes correctos al restar meses

date_correct.php

<?php
/*     date_correct.php
   
       Copyright 2010 mishudark <mishudark@astrata.com.mx> <moonsadly@gmail.com>
       
       This program is free software; you can redistribute it and/or modify
       it under the terms of the GNU General Public License as published by
       the Free Software Foundation; either version 2 of the License, or
       (at your option) any later version.
       
       This program is distributed in the hope that it will be useful,
       but WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
       GNU General Public License for more details.
       
       You should have received a copy of the GNU General Public License
       along with this program; if not, write to the Free Software
       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
       MA 02110-1301, USA.

  sirve para cuando vas restando meses al mes actual, ejem:
  2010-09 - 15 meses;
  restamos los meses: 09 - 15 = -6, ese -6 lo mandamos, junto con el año:
  list($year,$month) = date_correct(2010,-6);
*/

function  date_correct($year,$month){
  if($month < 1){
    $lessYear = floor( ($month-12)/-12 );
    $year -= $lessYear;
    $s = abs($month) % 12; //meses q se restaran a diciembre
    $month = 12-$s;
  }

  return array($year,$month);//retorna año y mes
}
?>