root/sanity_check.php

<?php
    require_once "functions.php";

    define('EXPECTED_CONFIG_VERSION', 17);
    define('SCHEMA_VERSION', 41);

    if (!file_exists("config.php")) {
        print __("<b>Fatal Error</b>: You forgot to copy 
        <b>config.php-dist</b> to <b>config.php</b> and edit it.\n");
        exit;
    }

    require_once "config.php";

    if (CONFIG_VERSION != EXPECTED_CONFIG_VERSION) {
        $err_msg = __("config: your config file version is incorrect. See config.php-dist.\n");
    }

    if (defined('RSS_BACKEND_TYPE')) {
        print __("<b>Fatal error</b>: RSS_BACKEND_TYPE is deprecated. Please remove this
            option from config.php\n");
        exit;
    }

    if (file_exists("xml-export.php") || file_exists("xml-import.php")) {
        print __("<b>Fatal Error</b>: XML Import/Export tools (<b>xml-export.php</b>
        and <b>xml-import.php</b>) could be used maliciously. Please remove them 
        from your TT-RSS instance.\n");
        exit;
    }

    if (SINGLE_USER_MODE && DAEMON_UPDATE_LOGIN_LIMIT > 0) {
        print __("<b>Fatal Error</b>: Please set DAEMON_UPDATE_LOGIN_LIMIT
            to 0 in single user mode.\n");
        exit;
    }

    if (USE_CURL_FOR_ICONS && ! function_exists("curl_init")) {
        print __("<b>Fatal Error</b>: You have enabled USE_CURL_FOR_ICONS, but your PHP 
            doesn't seem to support CURL functions.");
        exit;
    } 

    if (!defined('SESSION_EXPIRE_TIME')) {
        $err_msg = __("config: SESSION_EXPIRE_TIME is undefined");
    }

    if (SESSION_EXPIRE_TIME < 60) {
        $err_msg = __("config: SESSION_EXPIRE_TIME is too low (less than 60)");
    }

    if (SESSION_EXPIRE_TIME < SESSION_COOKIE_LIFETIME) {
        $err_msg = __("config: SESSION_EXPIRE_TIME should be greater or equal to" .
            "SESSION_COOKIE_LIFETIME");
    }

/*    if (defined('DISABLE_SESSIONS')) {
        $err_msg = "config: you have enabled DISABLE_SESSIONS. Please disable this option.";
} */

    if (DATABASE_BACKED_SESSIONS && SINGLE_USER_MODE) {
        $err_msg = __("config: DATABASE_BACKED_SESSIONS is incompatible with SINGLE_USER_MODE");
    }

    if (DATABASE_BACKED_SESSIONS && DB_TYPE == "mysql") {
        $err_msg = __("config: DATABASE_BACKED_SESSIONS are currently broken with MySQL");
    }

    if (defined('MAIL_FROM')) {
        $err_msg = __("config: MAIL_FROM has been split into DIGEST_FROM_NAME and DIGEST_FROM_ADDRESS");
    }

    if (!defined('COUNTERS_MAX_AGE')) {
        $err_msg = __("config: option COUNTERS_MAX_AGE expected, but not defined");
    }

    if (defined('DAEMON_REFRESH_ONLY')) {
        $err_msg = __("config: option DAEMON_REFRESH_ONLY is obsolete. Please remove this option and read about other ways to update feeds on the <a href='http://tt-rss.spb.ru/trac/wiki/UpdatingFeeds'>wiki</a>.");

    }

    if ($err_msg) {
        print "<b>".__("Fatal Error")."</b>: $err_msg\n";
        exit;
    }

?>