显示结果的历史记录

Question

我想在程序结尾显示计算结果作为列表。在每个帖子之后，结果将添加到先前结果列表中。 简单地说，我想显示完成计算结果的历史记录。

<form method="post" >

    <p>A:<input value="<?php echo $_POST['num1']?>" min="0" max="1000" type="number" name="num1"></p>
    <p>B:<input value="<?php echo $_POST['num2']?>" min="0" max="1000" type="number" name="num2"></p>
    <p>
        <select name="op">
            <option value="jaam">+</option>
            <option value="zarb">*</option>
            <option value="taghtsim">/</option>
            <option value="tafrigh">-</option>
        </select>
    </p>
<input type="submit" name="">
<hr>
</form>




<?php
    if (isset($_POST['num1']) && isset($_POST['num2']) && isset($_POST['op']))
    {
        switch ($_POST['op'])
        {
            case 'jaam':
                $r = $_POST['num1'] + $_POST['num2'];
                break;
            case 'zarb':
                $r = $_POST['num1'] * $_POST['num2'];
                break;
            case 'taghtsim':
                $r = $_POST['num1'] / $_POST['num2'];
                break;
            case 'tafrigh':
                $r = $_POST['num1'] - $_POST['num2'];
                break;
            default:
                $r = "Error!";
                break;
        }
    }
?>