Wow - the main site has to be one of the most Opera-hostile pages I've ever seen. Everything flickers as I move the mouse over the text, and the login pops in and out for no apparent reason...
As long as the mouse stays out of the page it displays just fine, though.
The bulk of it was caused by the fact we had an element which was only visible on-hover (a drop-down sign in menu) and within that element was an unclosed <label> tag. Because the label was unclosed, the rest of the page was being trapped in the <label> element which meant the lower half of the page only displayed when the parent element was visible (thus causing the flickering effect as the element was shown/hidden).
A lot of the caching we're doing is just plain key/value and so it was easier to just increase our usage of Memcached (we were already using Memcached at the time). If we need to store more complex structures in memory (e.g. lists) then Redis will be high on the list of choices.
Since I wrote this piece, we've been looking in to reworking our notifications and activity feeds so there's a good possibility that we will be looking in to Redis again.
The main problem that I have with PHP the language is the ugliness and weirdness of the syntax. Something like CoffeeScript for PHP, that compiles to PHP (but with nicer syntax), could help alleviate that.
That would break the biggest advantage of PHP (which granted, is already fading), which is the ability to immediately and effortlessly deploy scripts to basically any web host in the universe.
Yeah, unfortunately we were using an early open-source project to handle the real-time aspect of Prompt and when we needed to upgrade socket.io (one of the project's dependencies) to support the newer Web Socket protocol, it broke the app.
