<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "wypozyczalnia";

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

if ($conn->connect_error) {
   echo "Not connected, error: " . $mysqli_connection->connect_error;
}
echo '<input ', (isset($IDklienta['IDklienta']) ? 'value="'.$IDklienta['IDklienta'].'"' : ''), '/>' ;
echo "</br>";
 $result = mysqli_query($conn,"SELECT * FROM klienci");

    if($row = mysqli_fetch_array($result))
      {
          echo "<tr>";
          echo "<td>";
          echo "Imie: ";
      echo $row['Imie'];
          echo "</td>";
          echo "</br>";
          echo "<td>";
          echo "Nazwisko: ";
          echo $row['Nazwisko'];
          echo "</td>";
          //these are the fields that you have stored in your database table employee
      echo "</br>";
          echo "</tr>";
      }

    mysqli_close($conn);
    ?>