<?php


$dbServer = 'localhost';
$dbUser = 'root';
$dbPassword = '';
$dbName = 'klient';

$connection = new mysqli($dbServer, $dbUser, $dbPassword, $dbName);

$sql = " INSERT INTO users(
  username, email) VALUES
  ('jan', 'jan@gmail.com'),
  ('janusz', 'janusz@gmail.com'),
  ('krzys', 'krzys@gmail.com')
    ;";

if($connection ->query($sql) === TRUE){
    echo "dodano userów";
}

    else { echo "nie udało się".$connection->error ;
}
$connection->close();
?>