?php
/**
 * Created by PhpStorm.
 * User: ITAK
 * Date: 2017/3/3
 * Time: 10:28
 */
 error_reporting(E_ALL  ~E_NOTICE);
 if(isset($_POST['submit'])){
 $ok = true;
 $error = "出現的問題：br>";
 if($_POST['num1'] == ""){
  $ok = false;
  $error = $error."第一個數字不能為空br>";
 }
 else{
  if(!is_numeric($_POST['num1'])){
  $ok = false;
  $error = $error."第一個數字不是數字br>";
  }
 }
 if($_POST['num2'] == ""){
  $ok = false;
  $error = $error."第二個數字不能為空br>";
 }
 else{
  if(!is_numeric($_POST['num2'])){
  $ok = false;
  $error = $error."第二個數字不是數字br>";
  }
 }
 }
 if($ok){
 $sum = "";
 $fuhao = $_POST['fuhao'];
 if($fuhao == '+')
  $sum = $_POST['num1'] + $_POST['num2'];
 if($fuhao == '-')
  $sum = $_POST['num1'] - $_POST['num2'];
 if($fuhao == '*')
  $sum = $_POST['num1'] * $_POST['num2'];
 if($fuhao == '/')
  $sum = $_POST['num1'] / $_POST['num2'];
 if($fuhao == '%')
  $sum = $_POST['num1'] % $_POST['num2'];
 }
 echo "br>";
?>
html>
 head>
 meta charset="UTF-8">
 title>簡單計算器/title>
 /head>
 body>
 table border="0" width="400" align="center">
 form action="cal.php" method="post">
  caption>h1>簡單計算器/h1>/caption>
  tr>
  td>
   input type="text" size="5" name="num1" value="?php echo $_POST['num1'] ?>"/>
  /td>
  td>
   select name="fuhao">//下拉列表
   option ?php if($_POST['fuhao']=="+") echo "selected"?>
    value="+"> + /option>
   option ?php if($_POST['fuhao']=="-") echo "selected"?>
    value="-"> - /option>
   option ?php if($_POST['fuhao']=="*") echo "selected"?>
    value="*"> * /option>
   option ?php if($_POST['fuhao']=="/") echo "selected"?>
    value="/"> / /option>
   option ?php if($_POST['fuhao']=="%") echo "selected"?>
    value="%"> % /option>
   /select>
  /td>
  td>
   input type="text" name="num2" size="5" value="?php echo $_POST['num2'] ?>"/>
  /td>
  td>
   =
  /td>
  td>
   input type="text" name="res" size="5" value="?php echo $sum ?>"/>
  /td>
  /tr>
  tr align="center">
  td>
   input type="submit" value="計算" name="submit">
  /td>
  /tr>
  br>
  tr>
  td colspan="4">
   ?php
   if($ok){
    echo "結果為: {$_POST['num1']} {$_POST['fuhao']} {$_POST['num2']} = {$sum}";}
   else{
    echo $error;}
   ?>
  /td>
  /tr>
 /form>
 /table>
 /body>
/html>