projekt/php/get_classes.php

<?php
$dbhost = "localhost";
$dbuser = "root";
$dbpass = "";
$dbname = "ocena_zachowania";

$con = mysqli_connect($dbhost, $dbuser, $dbpass, $dbname);

if (!$con) {
    die("Błąd połączenia z bazą danych: " . mysqli_connect_error());
}

$ans = mysqli_query($con, "SELECT * FROM klasy;");
$json = array();

while($row = mysqli_fetch_assoc($ans)) {
    $json[] = $row;
}

echo json_encode($json);
?>