src/Bot.php
public function onSubscribe(\Closure $handler)
    {
        $this->managers[] = new Manager(function (Event $event) {
            return ($event instanceof \Viber\Api\Event\Subscribed);
        }, $handler);

        return $this;
    }
public function onSubscribe(\Closure $handler)
    {
        $this->managers[] = new Manager(function (Event $event) {
            return ($event instanceof \Viber\Api\Event\Subscribed);
        }, $handler);

        return $this;
    }
public function onSubscribe ( \ Closure $ handler ) { $ this -> managers [ ] = new Manager ( function ( Event $ event ) { return ( $ event instanceof \ Viber \ Api \ Event \ Subscribed ) ; } , $ handler ) ; return $ this ; }
Register subscrive event handler

@param  Closure $handler valid function
@return \Viber\Bot
Register subscrive event handler