从mysql返回的数据是乱码

-- 设置数据库字符集
ALTER DATABASE your_database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;

-- 设置表字符集
ALTER TABLE your_table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

-- 设置列字符集
ALTER TABLE your_table_name MODIFY your_column_name VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

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

mysqldump --default-character-set=utf8mb4 -u username -p database_name > dump.sql

mysql --default-character-set=utf8mb4 -u username -p database_name < dump.sql

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

// 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 * FROM your_table_name";
$result = $conn->query($sql);

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