$servername = "localhost";
$username = "root";
$password = "";
$dbname = "stackoverflow";
$conn = new mysqli($servername, $username, $password, $dbname);
$conn->set_charset("utf8");

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

$sql = " INSERT  INTO stackoverflow (user) VALUES ('alex')";
$conn->query($sql);

$sql = "SELECT user FROM WHERE stackoverflow = 'alex' ";