handler_blitz.php

<?php header("Content-type: text/html; charset=utf-8"); ?>
<?php
    $link = mysqli_connect("localhost", "db", "password");

    if (!$link) {
        die('Ошибка подключения (' . mysqli_connect_errno() . ') '
        . mysqli_connect_error());
    }
    
    mysqli_set_charset($link, "utf8");

    mysqli_select_db($link, "db");

    $data = mysqli_query($link, "SELECT * FROM `blitz` WHERE `id` = '$_POST[id]'");
    $row = mysqli_fetch_array($data, MYSQLI_ASSOC);
    if ($row) {
         if ($row['score'] < $_POST[score]) {
             mysqli_query($link, "UPDATE `blitz` SET `score` = '$_POST[score]', `time` = '$_POST[time]' WHERE `id` = '$_POST[id]'");
         } else if ($row['score'] == $_POST[score] and $row['time'] > $_POST[time]) {
             mysqli_query($link, "UPDATE `blitz` SET `time` = '$_POST[time]' WHERE `id` = '$_POST[id]'");
         }
    } else {
        mysqli_query($link, "INSERT INTO `blitz` (`score`, `time`, `id`, `name`, `photo_url`) VALUES ('$_POST[score]', '$_POST[time]', '$_POST[id]', '$_POST[name]', '$_POST[photo_url]')") or die(mysqli_error($link));
    }
    mysqli_close($link);
?>