如何在PHP中实现员工考勤数据的汇总统计？

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "attendance";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

echo "连接成功";
?>

<?php
// 获取员工ID、姓名、考勤日期、上班时间和下班时间
$id = $_POST['id'];
$name = $_POST['name'];
$date = $_POST['date'];
$time_in = $_POST['time_in'];
$time_out = $_POST['time_out'];

// 准备插入数据的SQL语句
$sql = "INSERT INTO attendance (id, name, date, time_in, time_out)
VALUES ('$id', '$name', '$date', '$time_in', '$time_out')";

// 执行SQL语句
if ($conn->query($sql) === TRUE) {
    echo "考勤数据插入成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

// 关闭数据库连接
$conn->close();
?>

<?php
// 获取要统计的月份
$month = $_POST['month'];

// 准备查询的SQL语句
$sql = "SELECT name, COUNT(*) AS attendance_days
        FROM attendance
        WHERE MONTH(date) = '$month'
        GROUP BY name";

// 执行SQL查询
$result = $conn->query($sql);

// 输出查询结果
if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        echo "员工：" . $row["name"]. "出勤天数：" . $row["attendance_days"]. "<br>";
    }
} else {
    echo "暂无考勤数据";
}

// 关闭数据库连接
$conn->close();
?>