What is PHP?
PHP is a powerful language tool for programmers that enables us to write websites with inbuilt functionality more quickly. We can now set the site to (safely*) update itself each day with new content.
*safely = when we update a website, it is not always guarenteed that the update will clear out backbone cached copies. The web was designed more as a library, not a transaction system.
The demands of Dynamic content dictates we adopt a modern way around the nature of the web. We must generate pages "on the fly" and tell the cache to ignore what we generate.
Image heavy pages are still cached, but the trend is more text and less image with reliably and uniformly presented dynamic content. It is best to frame the home page, have a clear and concise "splash page", and a sophisiticated inner layer that allows you to control your content, even if your updates are sporadic, you want them to be reliable.
We have explored many methods of exploiting the web productively and most people do not realise that there are many many ways of making a web page that works 100% of the time. But there are many more mistakes borne out of technical fear.