当我执行if条件时，切换情况值传递不工作

这是我用来显示下拉值的代码:

 switch ($_POST['input_102']) {
     case 14:
            $mailling=$mailling.'<li>Priority mail (domestic/US only)   <span>$14.00</span></li> ';
        break;
     case 40:
            $mailling=$mailling.'<li>Courier/Express (domestic/US only) <span>$40.00</span></li> ';
        break;
     case 14:
             $mailling=$mailling.'<li>Air Mail (overseas/international) <span>$14.00</span></li> ';
         break;
     case 80:
            $mailling=$mailling.'<li>Courier/Express (overseas/international) <span>$80.00 </span></li> ';
         break;
 }

这里我遇到了一个问题，我有两个值，比如14。所以我像这样修改了代码。它执行了，但是当if语句执行时，它什么也不显示，而else语句则显示结果:

 switch ($_POST['input_102']) {
       case 14:
             //custom code
            if($_POST['input_13']=='United States'){
                $mailling=$mailling.'<li>Priority mail (domestic/US only)   <span>$14.00</span></li> ';
             }else{
                $mailling=$mailling.'<li>Air Mail (overseas/international) <span>$14.00</span></li> ';
             }
              //custom code end 
           break;
       case 40:
             $mailling=$mailling.'<li>Courier/Express (domestic/US only) <span>$40.00</span></li> ';
           break;
       case 80:
             $mailling=$mailling.'<li>Courier/Express (overseas/international) <span>$80.00 </span></li> ';
           break;
  }                 

我打印了$_POST['input_13']，它的值是美国。为什么我没有得到if的结果