2014.01.07php简单计算器制作

<?php
  header('content-type:text/html;charset=utf-8');
  $num1=true; //判断是否为真
  $num2=true; //判断是否为真
  $message=""; //设置为空
  if(isset($_GET['submit'])){
         if($_GET['num1']==''){
             $num1=false;
             $message.='第一个数字不能为空';
         }
         if($_GET['num2']==''){
             $num2=false;
             $message.='第二个数字不能为空';
         }
        if($num1 && $num2){
            $sum=0;
            switch($_GET['ysf']){
                case '+':
                $sum=$_GET['num1']+$_GET['num2'];
                break;
                case '-':
                $sum=$_GET['num1']-$_GET['num2'];
                break;
                case 'x':
                $sum=$_GET['num1']*$_GET['num2'];
                break;
                case '/':
                $sum=$_GET['num1']/$_GET['num2'];
                break;
            }
        }
  }
 
  /*计算机制作*/
 ?>
 <table align="center" border="1" width="500">
     <caption><h1>计算机</h1></caption>
     <tr>
       <form action="jsq.php">
         <td>
             <input type='text' name='num1' value=''/>
        </td>
        <td>
             <select name="ysf">
                 <option>+</option>
                 <option>-</option>
                 <option>x</option>
                 <option>/</option>

             </select>
        </td>
        <td>
            <input type='text' name='num2' value=''/>
        </td>
        <td>
            <input type='submit' name='submit' value='计算'/>
        </td>
       </form>
     </tr>
 <?php 
     if(isset($_GET['submit']))
     {
       
        if($num1 && $num2){
        echo"<tr><td colspan='5'>";
         echo"计算结果为".$sum;
         echo"</td></tr>";
        }
        else{
         echo"<tr><td colspan='5'>";
         echo $message;
         echo"</td></tr>";
       }
     }
     

?>
 </table>

注意：if(isset($_GET['submit']))书写