Php计算器打印出数字而不是结果 - Php calculator printing out numbers instead of result

Php calculator printing out numbers instead of result

本文关键字：结果数字计算器打印 Php | 更新日期: 2023-09-27

我的php正在打印数字而不是结果。例如，它将打印出"3+3"而不是"6"。

我做错了什么？有人可以解释一下 php 如何读取代码以及我如何修复它。- 新的初学者学习PHP

        <?php
            //Check to see if the submit button got posted
            if(isset($_POST['submit'])){
                //If it did, get the values from the textbox
                $first_number = $_POST['first_number'];
                $second_number= $_POST['second_number'];
                $operator = $_POST['operator'];
                //Check to see if they are empty
                if(!empty($first_number) && !empty($second_number)){
                    echo $first_number . $operator . $second_number;
                    }
                else {
                    echo 'Please fill out all the forms';
                }
            }
        ?>
 </head>
    <body>
        <div id='wrap'> 

            <header id='header'>
                <h1> This Is A Simple Math Calculator </h1>
            </header>
            <section id='main'>
                <form action='math.php' method='POST'>
                <table cellspacing='10px'>
                    <tr>
                        <td>
                        <input type='text' name='first_number' placeholder='First Number'  size='15px'/>
                        </td>
                        <td>
                            <select name='operator'>
                                <option value='+'>+</option>
                                <option value='-'>-</option>
                                <option value='*'>*</option>
                                <option value='/'>/</option>
                                <option value='%'>%</option>
                            </select>
                        </td>
                        <td>
                            <input type='text' name='second_number' placeholder='Second Number' size='15px' />
                        </td>
                        <td>
                            <input type='submit' name='submit' value='=' />
                        </td>
                        <td>
                            <input type='text' name='answer' placeholder='' size='10px' />
                        </td>
                    </tr>
                </table>
                </form>
            </section>
            <footer>
                <p> MADE BY @KD </p>
            </footer>

既然你是初学者，你可以这样构建它

  if($operator == "+"){
     echo $first_number + $second_number;
  }
  if($operator == "-"){
     echo $first_number - $second_number;
  }
  // same for other operators you permit.

更改

echo $first_number . $operator . $second_number;

自

echo eval("echo $first_number$operator$second_number ;");

echo $result = eval('return '.$first_number . $operator . $second_number.';');