New code (optimizations/simplifications):

class Users {
    private static $key, $table, $logtable;

    public static function init($key) {
        self::$key = $key;
        self::$table = DBPREFIX.$key.'s';
        self::$logtable = self::$table.'_access_log';
    }

    public static function isLogged() {
        if(isset($_SESSION[self::$key]) and isset($_SESSION[self::$key]['uid'])) { # Combined ifs
            $uid = intval($_SESSION[self::$key]['uid']);
            $user = DB::select()->from(self::$table)->where('id', '=', $uid)->execute()->object();
            return count($user) > 0; # Simplified
        }
        return false; # Removed unnecesary elses
    }

    public static function userExist($login) {
        $user = DB::select()->from(self::$table)->where('login', '=', $login)->execute()->object();
        return count($user) > 0; # Simplified
    }

    public static function getUser($login) {
        $user = DB::select()->from(self::$table)->where('login', '=', $login)->execute()->object();
        if(count($user) > 0) {
            return $user[0];
        }
        return false; # Removed unnecessary else
    }

    public static function generateHash($password) {
        $salt = self::generateSalt();
        $hashedPassword = crypt($password, $salt);
        return array('hashed_password' => $hashedPassword, 'salt' => $salt);
    }

    private static function generateSalt($blowfishPre = '$2y$10$', $blowfishEnd = '$', $allowedChars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789./', $saltLength = 20) { # Added arguments for future customization
        $charsLength = strlen($allowedChars);
        $salt = "";
        for($i=0; $i < $saltLength; $i++)
        {
            $salt .= $allowedChars[mt_rand(0,$charsLength)];
        }
        return $blowfishPre . $salt . $blowfishEnd; # Removed unnecessary variable
    }

    public static function comparePasswords($input, $uid) {
        $user = DB::select()->from(self::$table)->where('id', '=', $uid)->execute()->object();
        if(count($user) > 0) {
            $user = $user[0];
            $password = $user->password;
            return crypt($input, $password) === $password;
        }
        return false; # Removed unnecessary else
    }

    public static function userExit() {
        if(isset($_SESSION[self::$key])) {
            unset($_SESSION[self::$key]);
        }
    }

    public static function changePassword($password, $uid) {
        $newPassword = self::generateHash($password);
        if(isset($newPassword['hashed_password']) && isset($newPassword['salt'])) {
            DB::update(self::$table)->set(array('password' => $newPassword['hashed_password'], 'salt' => $newPassword['salt']))->where('id', '=', $uid)->execute();
        }
    }

    public static function updateTime($uid) {
        DB::update(self::$table)->set(array('last_login' => time()))->where('id', '=', $uid)->execute();
    }

    public static function writeAccessLog($uid, $success) {
        DB::insert(self::$logtable)->set(array('admin_id' => $uid, 'date' => time(), 'success' => $success ? '1' : '0'))->execute(); # Inlined success var.
    }
}