<?php
header('content-type:text/html;charset=utf-8');
$rea=$_POST['a'];
$reb=$_POST['b'];
$re=$rea+$reb;
if($_POST['submit']){
echo "我算出来了，结果是:$re";
}else{
echo '<title>加法计算</title>
<form action="index.php" method="POST">
<input type="text" name="a"><br><input type="text" name="b"><br><center><input type="submit" name="submit" value="计算"></from>';}
?>