Well, I use both... I feel exactly the same comfort with both... Granted that HTML is a beginning language henceforth is easier to code with, PHP is amazing for creating CMS' and much much more, and as people have said before HTML is a Markup Language (Hypertext Markup Language to be exact

) and PHP is as squid said backend. Both have very versatile functions, and can be used to make amazing web pages, but when used together with JS and CSS they are amazing...
-Coolprogram