用php实现简单的自制计算器

存档：
 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <title>PHP实现计算器</title>
 5     </head>
 6     
 7     <body>
 8         <?php
 9             $mess = "";
10             if(isset($_POST["sub"])){
11                 if($_POST["num1"] == ""){
12                     $mess .= "第一个数不能为空!<br>";
13                 }
14                 else{
15                     if(!is_numeric($_POST["num1"])){
16                         $mess .="第一个数必须是数字!<br>";
17                     }
18                 }
19             
20                 if($_POST["num2"]==""){
21                     $mess .="第二个数不能为空!<br>";
22                 }
23                 else{
24                     if(!is_numeric($_POST["num2"])){
25                         $mess .="第二个数必须是数字!<br>";
26                     }
27                     else{
28                         if($_POST["opt"]=="/"&&$_POST["num2"]==0){
29                             $mess .="除数不能为0";
30                         }
31                     }
32                 }
33             }
34         ?>
35 <table border="1" align="center" width="400">
36     <form action="" method="post">
37         <caption><h1>计算器</h1></caption>
38         <tr>
39             <td>
40                 <input type="text" size="4" name="num1" value="<?php echo $_POST["num1"]?>" />
41             </td>
42             
43             <td>
44                 <select name="opt">
45                     <option value="+" <?php echo $_POST["opt"]=="+" ? "selected" : "" ?>>+</option>
46                     <option value="-" <?php echo $_POST["opt"]=="-" ? "selected" : "" ?>>-</option>
47                     <option value="x" <?php echo $_POST["opt"]=="x" ? "selected" : "" ?>>x</option>
48                     <option value="/" <?php echo $_POST["opt"]=="/" ? "selected" : "" ?>>/</option>
49                     <option value="%" <?php echo $_POST["opt"]=="%" ? "selected" : "" ?>>%</option>
50                 </select>
51             </td>
52             
53             <td>
54                 <input type="text" size="4" name="num2" value="<?php echo $_POST["num2"]?>" />
55             </td>
56             
57             <td>
58                 <input type="submit" name="sub" value="计算" />
59             </td>
60         </tr>
61     </form>
62     <?php
63         if(isset($_POST["sub"])){
64             echo '<tr><td colspan="4">';
65             if(!$mess){
66                 $sum=0;
67                 switch($_POST["opt"]){
68                     case "+":
69                         $sum = $_POST["num1"] + $_POST["num2"];
70                         break;
71                     case "-":
72                         $sum = $_POST["num1"] - $_POST["num2"];
73                         break;
74                     case "x":
75                         $sum = $_POST["num1"] * $_POST["num2"];
76                         break;
77                     case "/":
78                         $sum = $_POST["num1"] / $_POST["num2"];
79                         break;
80                     case "%":
81                         $sum = $_POST["num1"] % $_POST["num2"];
82                         break;
83                 }
84                 
85                 echo "结果:{$_POST['num1']} {$_POST['opt']} {$_POST['num2']} = {$sum}";
86             }
87             else{
88                 echo $mess;
89             }
90             echo '</td></tr>';
91         }
92     ?>
93 </table>
94     </body>
95 </html>
结果如下：