$username = "test";

$db = new mysqli("localhost", "root", "", "test");
$stmt = $db->prepare('SELECT * FROM user WHERE username=?');
$stmt->bind_param('s', $username);
$stmt->execute();
echo $stmt->num_rows();
if ($stmt->num_rows() > 0){
echo "good";
} else {
echo "bad";
}

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test";


$conn = new mysqli($servername, $username, $password, $dbname);

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

$sql = "SELECT * FROM user WHERE username = '$username'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        echo "good";
    }
} else {
    echo "bad";
}

$conn->close();
?>

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test";


$conn = new mysqli($servername, $username, $password, $dbname);

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

$sql = "SELECT * FROM user WHERE username = 'tomukas'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // output data of each row
    while($row = $result->fetch_assoc()) {
        echo "good";
    }
} else {
    echo "bad";
}

$conn->close();
?>