$link = mysqli_connect("127.0.0.1", "my_user", "my_password", "my_db");

$servername = "localhost";
$username = "username";
$password = "password";

// Create connection
$conn = new mysqli($servername, $username, $password);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// Create database
$sql = "CREATE DATABASE myDB";
if ($conn->query($sql) === TRUE) {
    echo "Database created successfully";
} else {
    echo "Error creating database: " . $conn->error;
}

$conn->close();

$servername = "localhost";
$username = "username";
$password = "password";

// Create connection
$conn = mysqli_connect($servername, $username, $password);
// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// Create database
$sql = "CREATE DATABASE myDB";
if (mysqli_query($conn, $sql)) {
    echo "Database created successfully";
} else {
    echo "Error creating database: " . mysqli_error($conn);
}

mysqli_close($conn);

$root="root";
$root_password="root_password";

$user='newuser';
$pass='newpass';
$db="newdb";

try {
    $dbh = new PDO("mysql:host=$host", $root, $root_password);

    $dbh->exec("CREATE DATABASE `$db`;
            CREATE USER '$user'@'localhost' IDENTIFIED BY '$pass';
            GRANT ALL ON `$db`.* TO '$user'@'localhost';
            FLUSH PRIVILEGES;")
    or die(print_r($db->errorInfo(), true));

} catch (PDOException $e) {
    die("DB ERROR: ". $e->getMessage());
}