<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>简单的PHP计算器</title>
</head>
<body>
<form method="get" action="">
计算 <input type="text" name="zuo" value="<?php if(isset($_GET[‘submit‘])) echo $_GET[‘zuo‘];?>">
<select name="sel">
<option value="+" <?php if(isset($_GET[‘submit‘])){if($_GET[‘sel‘] == ‘+‘) echo "selected";} ?> >+</option>
<option value="-" <?php if(isset($_GET[‘submit‘])){if($_GET[‘sel‘] == ‘-‘) echo "selected";} ?> >-</option>
<option value="*" <?php if(isset($_GET[‘submit‘])){if($_GET[‘sel‘] == ‘*‘) echo "selected";} ?> >*</option>
<option value="/" <?php if(isset($_GET[‘submit‘])){if($_GET[‘sel‘] == ‘/‘) echo "selected";} ?> >/</option>
</select>
<input type="text" name="you" value="<?php if(isset($_GET[‘submit‘])) echo $_GET[‘you‘];?>">
<button name="submit" value=""> = </button>
<span style="margin-left: 1rem;">
<?php
if(isset($_GET[‘submit‘])){
function abc($a, $b,$c){
$result = 0;
switch($c){
case ‘+‘: return $result = $a+$b;break;
case ‘-‘: return $result = $a-$b;break;
case ‘*‘: return $result = $a*$b;break;
case ‘/‘:
if($b != 0){
return $result = $a/$b;
}die("除数不能为0");
break;
default: echo ‘出错！‘;break;
}
return $result;
}
$z = $_GET[‘zuo‘];
$y = $_GET[‘you‘];
$v = $_GET[‘sel‘];
$x = abc($z, $y, $v);
echo $x;
}
?>
</span>
</form>
</body>
</html>
原文：https://www.cnblogs.com/whales/p/12268955.html