Great. Now he knows two different languages and still has no ideas on what to use them on.
Terrible advice.
The correct time to learn a new language is when your current one isn't meeting your needs or when you've completed enough projects to have learned as much as possible from your current language and can start bringing in ideas from others. Endlessly learning new languages and never using them is completely backwards.
Just to offer an alternate perspective, I am a developer who spends most of his paid time working on PHP projects, either on a bespoke framework used by a company I work with and a whole lot of WordPress (I'm not a fan, but it is very easy to get well-paid remote work in this system).
In the last couple of years, I have learned a number of other languages and frameworks, mostly whatever the "hip" folks are using (Zend, RoR, Django, Ember, Backbone), and of these the only thing that really is useful on a day to day level has been the python scraping framework, Scrapy.
Each of these systems has brought me new ways to think about PHP and Javascript code that I never would thought about if I was solely intent on solving the problems I had at hand as best I could in the PHP idioms used by WordPress and this bespoke web framework.
For instance, I certainly wouldn't be as comfortable with the map functions if I hadn't done just that little bit of playing Haskell that I did.
So in my case, learning other idioms for programming, even those which I don't apply directly, has been tremendously useful in understanding better ways to work with the systems that I have to work with in a day-to-day situation.
Terrible advice.
The correct time to learn a new language is when your current one isn't meeting your needs or when you've completed enough projects to have learned as much as possible from your current language and can start bringing in ideas from others. Endlessly learning new languages and never using them is completely backwards.