我是PHP新手，我试图通过制作计算器来学习"if statement"，但最终出现了错误。显示的结果不正确，还请帮助建议如何在每次提交后清除输入。
<html !doctype>
<head>
<title>
</title>
</head>
<body>
<?php
error_reporting();
if(isset($_POST['submit'])) {
$num1 = $_POST['number1'];
$num2 = $_POST['number1'];
$action = $_POST['action1'];
if($action == "addition"){
$add = $num1 + $num2;
echo "your value is";
echo $add;
}
if($action == "subtraction"){
$sub = $num1 - $num2;
echo "your value is";
echo $sub;
}
if($action =="multipilcation"){
$multi = $num1 * $num2;
echo "your value is";
echo $multi;
}
if($action =="division"){
$divi = $num1 / $num2;
echo "your value is";
echo $divi;
}
}
?>
<form method='post' name='myform'>
Enter Number 1:<br>
<input type="number" name="number1" >
<br>
Enter Number 2:<br>
<input type="number" name="number2" >
<br>
choose operation<br>
<select name='action1'>
<option>addition</option>>
<option>subtraction</option>
<option>multipilcation</option>
<option>division</option>
</select>
<input type="submit" name="submit" value="submit">
</form>
</body>
<footer>
</footer>
</html>
您对两个变量使用了相同的number1，将其更改为number2
$num1 = $_POST['number1'];
$num2 = $_POST['number2'];
^
$action = $_POST['action1'];
1）您没有在<option></option>标记中传递任何值。
<select name='action1'>
<option value="addition">addition</option>>
<option value="subtraction">subtraction</option>
<option value="multipilcation">multipilcation</option>
<option value="division">division</option>
</select>
2） 将$num2 = $_POST['number1'];更改为$num2 = $_POST['number2'];
<?
if(isset($_POST['submit'])) {
$num1 = $_POST['number1'];
$num2 = $_POST['number2'];
$action = $_POST['action1'];
$num2 = $_POST['number1'];
chnace with：
$num2 = $_POST['number2'];
还为select中的选项标记添加value属性。
<option value="addition">addition</option>>
<option value="subtraction">subtraction</option>
<option value="multipilcation">multipilcation</option>
<option value="division">division</option>