php mysql中文乱码

-- 检查数据库字符集
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;

-- 检查数据表字符集
SHOW CREATE TABLE your_table_name;

-- 修改数据表字符集
ALTER TABLE your_table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

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

$dsn = "mysql:host=localhost;dbname=database;charset=utf8mb4";
$username = "username";
$password = "password";

try {
    $pdo = new PDO($dsn, $username, $password);
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}

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