用PHP面向对象做了一个计算器，在计算界面输入后，会转到CalProcess.php，但是不显示结果

MyCalView.php
<html>
<head>
<title>计算器</title>
<meta http-equiv="content-type" content="text/html;charset=utf-8"/>
</head>
<body>
<form action="CalProcess.php" method="post">
<table width="300px" border="0" >
<tr><td>第一个数</td><td><input type="text" name="num1"/></td></tr>
<tr><td>第二个数</td><td><input type="text" name="num2"/></td></tr>
<tr><td>运算符</td><td>
<select name="oper">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
</td></tr>
<tr><td colspan="2"><input type="submit" value="计算结果"></td></tr>
</table>
</form>
</body>
</html>CalProcess.php
<?php
require_once "OperService.class.php";
if(isset($_REQUEST['num1'])){
        $num1=$_REQUEST['num1'];
}
if(isset($_REQUEST['num2'])){
        $num2=$_REQUEST['num2'];
}
if(isset($_REQUEST['oper'])){
        $oper=$_REQUEST['oper'];
}
$operService=new OperService();
echo $operService->getResult($num1,$num2,$oper);
?>OperService.class.php
<?php
class OperService{
        public function getResult($num1,$num2,$oper){
                switch($oper){
                  case"+":
                         $res=$num1+$num2;
                         break;
                  case"-":
                         $res=$num1-$num2;
                         break;
                  case"*":
                         $res=$num1*$num2;
                         break;
                  case"/":
                         $res=$num1/$num2; 
                         break;
                  default:
                          echo "运算符不正常";
                }
        }
}
?>