Multi-OTP is a PHP class that can be used to authenticate and manage OTP user tokens for strong two-factor authentication. It can create, update, and delete tokens to authenticate users with one time passwords (OTP). The users' data are stored in files. The class can also check the user token using several algorithms: Mobile OTP (MOTP), OATH/HOTP (RFC 4226), and OATH/TOTP HOTP Time Based (RFC 4226 extension). It works with compatible software tokens (iPhone, Android, PalmOS, Nokia, and other Java J2ME capable phones) and hardware tokens (such as Feitian, ZyXEL, Authenex, or Seamoon). The multiotp command line utility is also provided, both in "compiled" form (for Windows) and in source code (for Linux or educational purpose). The multiotp command line can be combined with FreeRADIUS (under Linux) or the free TekRADIUS LT (under Windows) in order to have a powerful radius strong authentication server.