php 查询mysql乱码

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

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

// 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);
}

// 设置连接字符集
$conn->set_charset("utf8mb4");

// 查询数据
$sql = "SELECT id, name FROM mytable";
$result = $conn->query($sql);

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