删除数据后index.php数据表无法显示，点击删除按钮出现空白页

问题描述 #

我搭建了一个连接MySQL的表单系统，insert.php为表单页面，填写表单提交后数据可存入MySQL，且能在index.php中显示数据表。但点击删除按钮时页面会变成空白，完成删除操作后index.php也无法正常显示数据表。以下是相关代码：

index.php代码 #

<?php
session_start();

if (isset($_POST["submit"])) {
    $ime = $_POST["ime"];
    $prezime  = $_POST["prezime"];
    $pozicija  = $_POST["pozicija"];

    if (!empty($ime) && !empty($prezime) && !empty($pozicija)) {
        /*host, username, password, dbname*/
        $link = mysqli_connect("localhost", "root", "", "forma");

        // Check connection
        if ($link === false) {
            die("ERROR: Could not connect. " . mysqli_connect_error());
        }

        // Attempt insert query execution
        $sql = "INSERT INTO forma (Ime, Prezime, Pozicija) VALUES ('$ime', '$prezime' , '$pozicija')";
        if (mysqli_query($link, $sql)) {
            echo "Records inserted successfully." . "<br>";
        } else {
            echo "ERROR: Could not able to execute $sql. " . mysqli_error($link);
        }

        $podaci = "SELECT * FROM forma";
        $rezultat = mysqli_query($link, $podaci);

        if (!$rezultat) {
            die(mysqli_error($link));
        }
        if (mysqli_num_rows($rezultat) > 0) {
            foreach ($rezultat as $rez) {
                foreach ($rez as $key => $value) {
                    echo ucfirst($key) . ": " . $value . "<br>";
                }
            }
        }

        // Close connection
        mysqli_close($link);
    }
} 
?>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <?php
    if (isset($_SESSION['status'])) {
    ?>
        <div class="alert alert-warning alert-dismissible fade show" role="alert">
            <strong>Hey!</strong> <?php echo $_SESSION['status']; ?>
            <button type="button" class="btn" data-bs-dismiss="alert" aria-label="Close"></button>
        </div>
    <?php
        unset($_SESSION['status']);
    }
    ?>
    <form action="delete.php" method="POST">
        <table class="table">
            <tbody>
                <tr>
                    <th>
                        <button type="submit" name="delete" class="btn-delete">Delete</button>
                    </th>
                    <th>ID</th>
                    <th>Ime</th>
                    <th>Prezime</th>
                    <th>Pozicija</th>
                </tr>
            </tbody>
            <tbody>
                <?php
                $con = mysqli_connect("localhost", "root", "", "forma");
                $query = "SELECT * FROM forma";
                $query_run  = mysqli_query($con, $query);

                if (mysqli_num_rows($query_run) > 0) {
                    foreach ($query_run as $row) {
                ?>
                        <tr>
                            <td>
                                <input type="checkbox" name="delete_id[]" value="<?= $row['ID']; ?>">
                            </td>
                            <td><?= $row['ID']; ?></td>
                            <td><?= $row['Ime']; ?></td>
                            <td><?= $row['Prezime']; ?></td>
                            <td><?= $row['Pozicija']; ?></td>
                        </tr>
                    <?php
                    }
                } else {
                    ?>
                    <tr>
                        <td colspan="5">No Record Found</td>
                    </tr>
                <?php
                }
                ?>
            </tbody>
        </table>
    </form>
</body>
</html>

insert.php代码 #

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Form</title>
</head>
<body>
    <form action="index.php" method="post">
        <label for="ime">Ime</label>
        <input type="text" name="ime" required><br>
        <label for="prezime">Prezime</label>
        <input type="text" name="prezime" required><br>
        <label for="pozicija">Pozicija</label>
        <input type="text" name="pozicija" required><br>
        <button type="submit" name="submit">Submit</button><br>
    </form>
</body>
</html>

delete.php代码 #

<?php
//delete
session_start();
$con = mysqli_connect("localhost", "root", "", "forma");

if (isset($_POST['delete']) && isset($_POST['delete_id']) && !empty($_POST['delete_id'])) {
    // 过滤ID为整数，防止SQL注入
    $all_id = array_map('intval', $_POST['delete_id']);
    $extract_id = implode(',', $all_id);

    $query = "DELETE FROM forma WHERE ID IN($extract_id) ";
    $query_run = mysqli_query($con, $query);

    if ($query_run) {
        $_SESSION['status'] = "Multiple Data Deleted Successfully";
        header("Location: index.php");
        exit();
    } else {
        $_SESSION['status'] = "Multiple Data Not Deleted: " . mysqli_error($con);
        header("Location: index.php");
        exit();
    }
} else {
    $_SESSION['status'] = "Please select at least one record to delete";
    header("Location: index.php");
    exit();
}
?>

问题根源分析 #

1. index.php逻辑范围错误：原代码中整个HTML页面和删除表单都被包裹在if (isset($_POST["submit"]))判断内，只有提交表单时才会渲染页面。删除后跳转回index.php时无submit参数，导致页面无输出，表现为空白。
2. 字段名拼写不一致：原SQL中使用Poziicija（多一个字母i），与表单字段pozicija、显示表头Pozicija不统一，可能导致数据显示异常或插入错误。
3. delete.php无空值处理：未判断是否选择了要删除的记录，若直接提交删除按钮，$_POST['delete_id']不存在会引发报错，导致页面空白。
4. session_start()位置错误：原index.php中session_start()放在HTML标签之后，会触发"headers already sent"警告，导致session提示信息无法正常显示。
5. SQL注入风险：原delete.php直接将用户输入的ID拼入SQL语句，存在安全隐患。

解决步骤总结 #

1. 拆分index.php逻辑：将插入数据的代码保留在if (isset($_POST["submit"]))内，HTML页面和数据展示部分移到判断外，确保页面始终能正常渲染。
2. 统一字段名：将所有SQL语句中的Poziicija改为Pozicija，保持与表单和表头一致。
3. 修复delete.php的空值判断：添加对$_POST['delete_id']的存在性和非空判断，避免无选择时报错。
4. 调整session_start()位置：将session_start()移到index.php的PHP代码最开头，确保在任何输出之前启动session。
5. 防范SQL注入：使用array_map('intval', ...)过滤ID为整数，避免恶意SQL注入。
6. 添加错误信息：在delete.php中加入mysqli_error($con)，便于排查删除失败的具体原因。

内容的提问来源于stack exchange，提问作者Hollyy