I'm currently re-writing my site using my own framework (it's very simple and does exactly what I need, i've no need for something like Zend or Cake PHP). I've done alot of work in making sure everything is cached properly, caching pages in files so avoid sql queries and generally limiting the number of sql queries.
Overall it looks like it's very speedy. The average time taken for the front page (taken over 100 times) is 0.046152 microseconds.
But one thing i'm not sure about is whether i've done enough to reduce php memory usage. The only time i've ever encountered problems with it is when uploading large files.
Using memory_get_peak_usage(TRUE), which I THINK returns the highest amount of memory used whilst the script has been running, the average (taken over 100 times) is 1572864 bytes.
Is that good?
I realise you don't know what it is i'm doing (it's rather simple, get the 10 latest articles, the comment count for each, get the user controls, popular tags in the sidebar etc). But would you be at all worried with a script using that sort of memory getting hit 50,000 times a day? Or once every second at peak times?
I realise that this is a very open ended question. Hopefully you can understand that it's a bit of a stab in the dark and i'm really just looking for some re-assurance that it's not going to die horribly come re-launch day.
