PHP表单值保留教程：提交与刷新后如何保持数据

<?php
$name = ""; // 初始化变量

// 检查表单是否提交
if (isset($_POST['submit'])) {
    // 如果提交，获取并转义Name字段的值
    $name = htmlspecialchars($_POST['Name']);
}
?>

<form method="POST">
    <div class="form-group">
        <label for="nameInput">姓名</label>
        <!-- 将$name的值赋给input的value属性 -->
        <input class="form-control" type="text" id="nameInput" name="Name" value="<?php echo $name; ?>" autocomplete="off" required />
    </div>
    <button type="submit" name="submit" class="btn btn-primary">提交</button>
</form>

<?php
$month = ""; // 初始化变量

// 检查表单是否提交
if (isset($_POST['submit'])) {
    // 如果提交，获取Month字段的值
    $month = $_POST['Month'];
}
?>

<form method="POST">
    <div class="form-group">
        <label for="monthSelect">月份</label>
        <select class="form-control" name="Month" id="monthSelect" required="required">
            <option value="">请选择月份</option>
            <!-- 根据$month的值动态添加selected属性 -->
            <option <?php if ($month == 'January') echo 'selected'; ?> value="January">一月</option>
            <option <?php if ($month == 'February') echo 'selected'; ?> value="February">二月</option>
            <option <?php if ($month == 'March') echo 'selected'; ?> value="March">三月</option>
            <option <?php if ($month == 'April') echo 'selected'; ?> value="April">四月</option>
            <option <?php if ($month == 'May') echo 'selected'; ?> value="May">五月</option>
            <option <?php if ($month == 'June') echo 'selected'; ?> value="June">六月</option>
            <option <?php if ($month == 'July') echo 'selected'; ?> value="July">七月</option>
            <option <?php if ($month == 'August') echo 'selected'; ?> value="August">八月</option>
            <option <?php if ($month == 'September') echo 'selected'; ?> value="September">九月</option>
            <option <?php if ($month == 'October') echo 'selected'; ?> value="October">十月</option>
            <option <?php if ($month == 'November') echo 'selected'; ?> value="November">十一月</option>
            <option <?php if ($month == 'December') echo 'selected'; ?> value="December">十二月</option>
        </select>
    </div>
    <button type="submit" name="submit" class="btn btn-primary">提交</button>
</form>

<?php
// 初始化变量
$name = "";
$month = "";

// 检查表单是否提交
if (isset($_POST['submit'])) {
    // 获取并处理表单数据
    $name = htmlspecialchars($_POST['Name']);
    $month = $_POST['Month'];

    // 可以在这里进行数据验证或保存到数据库等操作
    // 例如：
    // if (!empty($name) && !empty($month)) {
    //     echo "<p>表单提交成功！姓名: {$name}, 月份: {$month}</p>";
    // } else {
    //     echo "<p style='color:red;'>请填写所有必填项。</p>";
    // }
}
?>

<!DOCTYPE