PHP中怎么连接MySQL数据库

$servername="localhost";
$username="root";
$password="root";
$dbname="name1";
$link = mysqli_connect($servername, $username, $password, $dbname);
if (mysqli_connect_errno()) {
    printf("连接失败: %s\n", mysqli_connect_error());
    exit();
}
echo "连接成功".
"";

$host='localhost';
$dbname='name1';
$username='root';
$password='root';
$pdo=new PDO("mysql:host=$host;dbname=$dbname",$username,$password);
echo "连接成功"."
";
?>