engelsystem/includes/pages/guest_stats.php

<?php

function guest_stats()
{
    global $api_key;

    if (isset($_REQUEST['api_key'])) {
        if ($_REQUEST['api_key'] == $api_key) {
            $stats = [];

            list($user_count) = sql_select("SELECT count(*) AS `user_count` FROM `User`");
            $stats['user_count'] = $user_count['user_count'];

            list($arrived_user_count) = sql_select("SELECT count(*) AS `user_count` FROM `User` WHERE `Gekommen`=1");
            $stats['arrived_user_count'] = $arrived_user_count['user_count'];

            $done_shifts_seconds = sql_select_single_cell("SELECT SUM(`Shifts`.`end` - `Shifts`.`start`) FROM `ShiftEntry` JOIN `Shifts` USING (`SID`) WHERE `Shifts`.`end` < UNIX_TIMESTAMP()");
            $stats['done_work_hours'] = round($done_shifts_seconds / (60 * 60), 0);

            $users_in_action = sql_select("SELECT `Shifts`.`start`, `Shifts`.`end` FROM `ShiftEntry` JOIN `Shifts` ON `Shifts`.`SID`=`ShiftEntry`.`SID` WHERE UNIX_TIMESTAMP() BETWEEN `Shifts`.`start` AND `Shifts`.`end`");
            $stats['users_in_action'] = count($users_in_action);

            header("Content-Type: application/json");
            raw_output(json_encode($stats));
            return;
        }
        raw_output(json_encode([
            'error' => "Wrong api_key."
        ]));
    }
    raw_output(json_encode([
        'error' => "Missing parameter api_key."
    ]));
}