As your site traffic grows it takes longer and longer to generate a dynamic page from sending multiple queries to a database. One possible solution to limit queries is to cache the result of each query that is needed, or to have a complete full page cache for your site.

They look at the two ways I mentioned - the Cache_Lite PEAR package and the APC extension (that will soon be included by default in the stable PHP releases). Bits of code are provided for each showing how to get them set up and get them working inside of your application.

Nothing's cooler than writing a bad-ass site or application and watching it gain popularity and a significant user base. By the same token, nothing's more frustrating that watching your app fall on its face when its running under high load. [...] Before you say, "throw more / better hardware at that mo-fo", why not take a moment and learn about APC: Alternative PHP Cache...

He describes the caching software - what it is and how it can help you and your application - and includes examples using a CacheManger class to store and set values quickly and easily.

Some websites use other technologies like Java and face the exact same problems. There are different variables involved here and the most common one is database. So I thought i would post a couple of articles related to performance and tuning.

This this post of the series focuses on the first of the two - APC - and talks about places it's used and includes some general performance recommendations. These include "Don't try to throw everything at your poor database" and the importance of XDebug.

There's some good advice in there, and I thought it'd be a good idea to quickly add a bit more detail about the separate approaches that Mike raises.

He goes over the APC caching, memcache, the "gzip trick", the "Not Modified" header and optimized SQL statements.

He also mentions one thing that Mike didn't mention - a split between static files (no PHP needed) and their dynamic cousins. Having a more pure Apache (no PHP installed) can help give a minute jump in speed that, depending on the size of the site, could really add up from a user's perspective.