php 网站出现乱码

<?php
header('Content-Type: text/html; charset=utf-8');
?>

CREATE TABLE `example` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

<?php
header('Content-Type: text/html; charset=utf-8');
?>

<?php
$mysqli = new mysqli("localhost", "user", "password", "database");
$mysqli->set_charset("utf8mb4");
?>

<?php
// 设置HTTP响应头
header('Content-Type: text/html; charset=utf-8');

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

// 查询数据
$sql = "SELECT id, name FROM example";
$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();
?>