<?php
$conn = new mysqli("localhost", "root", "", "szkola");
$sql = "SELECT id, class_name FROM classes";
$result = $conn->query($sql);

$roles = [];
if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        $roles[] = $row;
    }
}

header('Content-Type: application/json');
echo json_encode($roles);
$conn->close();
?>