<?
$pkg['cp_billing_cycle'] = 3;
$pkg['cp_last_renew_year'] = '2005';
$pkg['cp_last_renew_month'] = '7';

$renewals = ceil(12 / $pkg['cp_billing_cycle']);

$last_renewal_year = $pkg['cp_last_renew_year'];
$next_renewal = $pkg['cp_last_renew_month'];

for($i = $renewals; $i >= 0; $i--)
{
  $next_renewal += $pkg['cp_billing_cycle'];
  if ($next_renewal > 12)
  {
    $next_renewal -= 12;
    $last_renewal_year += 1;
  }
 
  echo 'Month: '.$next_renewal.' Year: '. $last_renewal_year."\n";
} 

// This outputs:
/*
Month: 10 Year: 2005
Month: 1 Year: 2006
Month: 4 Year: 2006
Month: 7 Year: 2006
Month: 10 Year: 2006
*/
?>