PHP PDO 安全执行 set names utf8 的正确方法

<?phpdefine('DB_HOST', 'localhost');define('DB_SCHEMA', 'test');define('DB_USER', 'test');define('DB_PASSWORD', 'test');define('DB_ENCODING', 'utf8');$dsn = 'mysql:host=' . DB_HOST . ';dbname=' . DB_SCHEMA;$options = array(    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,);if( version_compare(PHP_VERSION, '5.3.6', '<') ){    if( defined('PDO::MYSQL_ATTR_INIT_COMMAND') ){        $options[PDO::MYSQL_ATTR_INIT_COMMAND] = 'SET NAMES ' . DB_ENCODING;    }}else{    $dsn .= ';charset=' . DB_ENCODING;}$conn = @new PDO($dsn, DB_USER, DB_PASSWORD, $options);if( version_compare(PHP_VERSION, '5.3.6', '<') && !defined('PDO::MYSQL_ATTR_INIT_COMMAND') ){    $sql = 'SET NAMES ' . DB_ENCODING;    $conn->exec($sql);}