<!DOCTYPE html>
<html>
<head>
<title>PHP简易计算器</title>
</head>
<body>
<?php
$mess = "";
if (isset($_POST["sub"])){
if ($_POST["num1"] == "") $mess .= "第一个数不能为空<br/>";
else if (!is_numeric($_POST["num1"])) $mess .= "第一个数必须是数字<br/>"; if ($_POST["num2"] == "") $mess .= "第二个数不能为空<br/>";
else if (!is_numeric($_POST["num2"])) $mess .= "第二个数必须是数字<br/>";
else if ($_POST["opt"]=="/" && $_POST["num2"] == 0) $mess .= "除数必须为0<br/>";
} ?>
<?php
//第一次访问时设置初始值
if (!isset($_POST["num1"]))$_POST["num1"] = "0";
if (!isset($_POST["num2"]))$_POST["num2"] = "0";
if (!isset($_POST["opt"]))$_POST["opt"] = "+";
// echo $_POST["num1"];
?>
<table align ="center" width="400">
<form action="" method="post">
<caption><h1>计算器</h1></caption>
<tr>
<td><input type="text" size="4" name="num1" value="<?php echo $_POST["num1"]?>"/></td>
<td>
<select name="opt">
<option value ="+" <?php echo $_POST["opt"]=="+"?"selected":"" ?>>+</option>
<option value ="-" <?php echo $_POST["opt"]=="-"?"selected":"" ?>>-</option>
<option value ="*" <?php echo $_POST["opt"]=="*"?"selected":"" ?>>*</option>
<option value ="/" <?php echo $_POST["opt"]=="/"?"selected":"" ?>>/</option>
</select>
</td>
<td><input type="text" size="4" name="num2" value="<?php echo $_POST["num2"]?>"/></td>
<td><input type="submit" name="sub" value="计算"/></td>
</tr> </form>
<?php
if(isset($_POST["sub"])) {
echo '<tr><td colspan="4">'; if(!$mess){
$sum = 0;
switch ($_POST["opt"]) {
case "+":$sum=$_POST["num1"]+$_POST["num2"];break;
case "-":$sum=$_POST["num1"]-$_POST["num2"];break;
case "*":$sum=$_POST["num1"]*$_POST["num2"];break;
case "/":$sum=$_POST["num1"]/$_POST["num2"];break;
}
echo "结果: {$_POST['num1']} {$_POST['opt']} {$_POST["num2"]} = {$sum}";
} else echo $mess; echo '</td></tr>';
}
?>
</table>
</body>
</html>
执行结果
