php mysql输出乱码问题

-- 查看当前数据库字符集
SHOW VARIABLES LIKE 'character_set_database';

-- 修改数据库字符集
ALTER DATABASE your_database_name CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

header("Content-Type: text/html; charset=utf-8");

$mysqli = new mysqli("localhost", "username", "password", "database");
$mysqli->set_charset("utf8mb4");

<?php
// 设置HTTP头字符集
header("Content-Type: text/html; charset=utf-8");

// 连接数据库并设置字符集
$mysqli = new mysqli("localhost", "username", "password", "database");
if ($mysqli->connect_error) {
    die("连接失败: " . $mysqli->connect_error);
}
$mysqli->set_charset("utf8mb4");

// 查询数据
$sql = "SELECT * FROM your_table";
$result = $mysqli->query($sql);

if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        echo "ID: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} else {
    echo "0 结果";
}
$mysqli->close();
?>