<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<?php
$n1 = "";
$n2 = "";
$result = "";
if( isset($_POST['num1']) )
{
$n1 = $_POST['num1'];
$n2 = $_POST['num2'];
$result = $n1 + $n2;
//echo "<br>计算结果为:" , $result;
}
?>
<body>
<!-- action留空表示提交给自己(本页) -->
<form action="" method="post">
数字1<input type="text" name="num1" value="<?php echo $n1; ?>">
<!-- 有兴趣有时间的同学,可以把这个"+"用一个select来代替,用户可以选择加减乘除 -->
+
数字2<input type="text" name="num2" value="<?php echo $n2; ?>">
<input type="submit" value="=">
<input type="text" name="result" value="<?php echo $result; ?>">
</form>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head