[ken]

Isn't that the blub paradox? What if there was an unknown-to-you language feature that you were implementing by hand, or worse, if you were avoiding an end-user feature entirely because it would be too much work and so you're not even considering it? How would you know if it could affect user experience or revenue if you don't know about it?

I've certainly used a language for a while, and then read the book on it, and said "oooh!", and then gone back and fixed all my old code. I could have saved a lot of time if I had known about that feature in the first place. (The extreme case are the posts on thedailywtf.com of people who don't know about loops, but there are much higher-level examples, too.)

That's not to say you can't run a perfectly usable and profitable startup knowing just a little bit of PHP (and as Larry says, more power to you!), but I don't know how one could claim that it has no effect.

[superasn]

In real world this isn't the case. First of all, when you're working on projects, you see that there are some things which you're doing over and over (like CRUD). Now at least in my opinion it is okay to create your first site by using mysql_real_escape_string like functions as long as by the end of the day it gets the job done. Because my priority as a small website owner is always getting new signups. And as far as I'm concerned, my lead does not care how I'm inserting his email into the database. But had I spend my time learning the proper MVC design, I maybe would have lost three precious months of leads which does indeed make a difference to my bank account.

Second of all nowadays you're never working alone (even when in fact you're working alone). What I mean is every programmer nowadays uses Google and StackOverflow to do a lot of his work. So when you're doing something wtf like using the mysql_real_escape_string, you maybe once in a while try to check how other programmers are doing it because maybe for you it takes too long or you're just stuck. And then you learn a thing or two about how to do is more easily. Still, it doesn't mean you have to become a great programmer of the language first, instead you just need to hone the things which you need the most for your business.