制作PHP计算器存储和显示历史记录

Question

I am new to PHP and I am trying to create a simple calculator that also displays the history (past calculations) in a div on the page.

You input something like "4+" in the first field and "3" in the second, and it displays "4+3=7" in the div called "results". However, I want to display the whole history of results there, so when I perform a new calculation, both calculations/results will be displayed the results div. What's the best way of doing this in PHP? Would DOMNode::appendChild be an option?

Here is my code this far:

<div id="form">
    <form action="" method="post">
        <input type ="text" name="firstNumber">
        <input type ="text" name="secondNumber">
        <input type ="submit" style="display:none">
    </form>
</div>

Result:

<?php 

    $number1 = $_POST["firstNumber"];
    $number2 = (int)$_POST["secondNumber"];

    @$operator = substr($number1, -1);


switch($operator){
    case '+':
        $result = (int)$number1+$number2;
        echo $result;
        break;
     case '-':
        $result = (int)$number1-$number2;
        echo $result;
        break;
    case '*':
        $result = (int)$number1*$number2;
        echo $result;
        break;
    case '/':
        $result = (int)$number1/$number2;
        echo $result;
        break;
}

?>


<div id="results">
    <?php echo substr($number1,0, -1);
        echo $operator; 
        echo $number2; ?>
 <br>=
    <?php echo $result; ?>
</div>

Thank you for helping out!

Answer 1

To store the history server-side, you'll either need a database, like MySQL, a caching server like Memcache or Redis, or you can just store the results in the $_SESSION. Here is a good resource on how to store data in the session. If you store it in $_SESSION, your history will be lost when the user clears their cookies (or logs out, if you implement user accounts).