Well, to be honest, I know very little PHP yet get by with my vague idea of it. I'm fairly strong in HTML, yet may HTML pages look like crap piled on rotten newspapers. I think you'll find most websites migrating to other forms of writing, such as PHP and XML rather than HTML. PHP is nice because of it's (ready for the 25 cent made up word) dynamocity
It's written to be dynamic, and can pull a lot of it's info from a database and such.
Anyway, back to the issue at hand, you don't have to really learn web design to run a webserver. However, to know what's going on behind the curtain will certainly help if things don't go right. Check out the page I listed above, and also look at:
to find out how to setup Apache to work with PHP so you can get that Gallery going!