Writing more efficient PHP
I found the IBM tutorial on writing more efficient PHP today. Most of it is very obvious stuff [cache values, understand the lower-level workings of the programming language in question so you can take advantage of it's design, etc, etc], says a guy with ten years experience of developing software with a variety of programming languages. But some is more cunning than obvious glaring-you-in-the-face-with-a-cheeky-smile stuff.
For example if too many GET requests are made then the web-application will seem to be much slower. So when generating PDFs, it’s good to issue both the Content-Type and the Content-Disposition headers to minimise the number of requests that the browser may make.
If you aren’t sure what’s going on in a scenario such as this and you use FireFox then you could always install the LiveHeaders plugin to have a detailed look what information and requests are traversing the connection between browser and server.
I recently discovered the memcached project as well. memcached is a distributed memory caching system like a huge big hash table shared between any mumber of servers intended for use in speeding up dynamic web applications by alleviating database load though it can be used for more generic purposes as well. I haven’t used it yet, but wish I had. It is used by Slashdot, WikiPedia and SourceForge amongst others.