SimpleCalculator

<?php
error_reporting(E_ALL & ~E_NOTICE);


if( isset($_POST['sub'])) {
$signal = true;
$errormess = "出现以下问题：<br>";


if($_POST['num1'] == ""){
$signal = false;
$errormess .= "第一个数不能为0！<br>";
}else{
if(!is_numeric($_POST['num1'])){
$signal = false;
                $errormess .= "第一个不是有效数字，请重新输入。<br>";
}
}
if($_POST['num2'] == ""){
                $signal = false;
$errormess .= "第二个数不能为0！<br>";
}else{
if(!is_numeric($_POST['num2'])){
$signal = false;
                $errormess .= "第二个不是有效数字，请重新输入。<br>";
}
}
if($signal){
$result = "";
switch($_POST['operator']) {
              case '+': $result = $_POST['num1'] + $_POST['num2'];break;
case '-': $result = $_POST['num1'] - $_POST['num2'];break;
case '*': $result = $_POST['num1'] * $_POST['num2'];break;
case '/': $result = $_POST['num1'] / $_POST['num2'];break;
case '%': $result = $_POST['num1'] % $_POST['num2'];break;
}
}
}
echo '<br>';
?>