php 文件乱码

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

<meta charset="UTF-8">

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

CREATE DATABASE mydatabase CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
CREATE TABLE mytable (
    id INT PRIMARY KEY,
    name VARCHAR(255)
) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

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

$mysqli = new mysqli("localhost", "user", "password", "database");
if ($mysqli->connect_error) {
    die("连接失败: " . $mysqli->connect_error);
}
$mysqli->set_charset("utf8mb4");

$sql = "SELECT id, name FROM mytable";
$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();
?>