In PHP, sessions can keep track of authenticated in users. They are an essential building block in today's websites with big communities and a lot of user activity. Without sessions, everyone would be an anonymous visitor. In system terms, PHP sessions are little files, stored on the server's disk. But on high traffic sites, the disk I/O involved, and not being able to share sessions between multiple webservers make this default system far from ideal. This is how to enhance PHP session management in terms of performance and shareability.

I used to use Dean Edwards Javascript Packer a lot to compress my Javascript sources. Libraries of 100kB could easily shrink to 30kB and that saves load times & bandwidth. A good writeup by Julien Lecompte made me realize that there were better ways.

Recently two of my articles reached the Digg frontpage at the same day. My web server isn't state of the art and it had to handle gigantic amounts of traffic. But still it served pages to visitors swiftly thanks to a lot of optimizations. This is how you can prevent heavy traffic from killing your server.

If you're running Squid to cache your website, you can use an htaccess file to control what kind of files should be cached, and for how long.

Let's say your site is becoming a big success and as a result it's becoming slower and slower. There are several things you do without buying additional hardware.

You want your website to be as safe as possible. So you'll typically want Open Basedir and Safe Mode to be on. When you're in a shared hosting environment, you'll find that any server administrator with a good sense of security will also have these restrictions in place. However security pretty much always limits functionality and this case is no different. Because what if you are caged in a restricted environment, and you would still like to use shared libraries like the ones provided by PEAR?

Readable URLs are nice. A well made website will have a logical layout, with intelligent folder and file names, and as few technical details as possible. In the most well designed sites, readers can guess at filenames with a high level of success. Clean URLs are great because they.