..............
$months = "";

       if ($d <= -7) {
              $months = "more than 7 months before launch";
      } else if ($d <= -4 && $d >= -6){
              $months = "6 to 4 months before launch";
      } else if ($d <= -1 && $d >= -3){
              $months = "3 to 1 months before launch";
      } else if ($d >= 0 && $d <= 3) {
              $months = "0 to 3 months";
      } else if ($d >= 4 && $d <= 6) {
              $months = "4 to 6 months";
      } elseif ($d >= 7 && $d <= 9) {
              $months = "7 to 9 months";
      } elseif ($d >= 10 && $d <= 12) {
             $months = "10 to 12 months";
      } elseif ($d >= 13 && $d <= 24) {
              $months = "1 up to 2 years";
      } elseif ($d >= 25 && $d <= 36) {
             $months = "more than 2 years up to 3 years";
      } elseif ($d >= 36 && $d <= 60) {
              $months = "more than 3 years up to 5 years";
      } elseif ($d >= 61) {
             $months = "more than 5 years";
      }
........