On the NetTuts.com site there's a new tutorial showing you how to introduce the Memcached tool to your application - a quick and easy way to cache data and optimize performance.

Your latest PHP/MySQL website is finally online. And it's awesome. But it's not as fast as you want it to be, because of the many SQL queries running every time a page is generated. And above that, you have the feeling it will not scale well under heavy loads. And you are most likely right. In this tutorial, we will see how you can greatly improve your website's responsiveness [...] by implementing a cache layer between your code and your database. The good news is it is fairly easy, and can be done in a few minutes!

They help you get the memcached server installed (a one-liner in most linux distributions) and how to install the memcached extension using PECL. Code is included showing you how to connect to the server, store data into the cache based on a generated key and how to pull the same data back out.

On the Leaseweb Labs blog there's a recent post looking at using the POC framework to work with flexible output caching. The tool makes it easy to create a new object and push cache content into it, automatically caching the data to sources like the file system, a Redis instance or a MongoDB database.

Last year at the Symfony conference in Paris I have heard a really good quote: "There are only two hard things in Computer Science: cache invalidation and naming things" - Phil Karlton. I agree with it and it gave me a boost to keep evolving the concept.

He includes an introduction to the caching features of the framework complete with sample code showing first how to cache to the default file system and a more complex example that uses unique caches and page blacklists. Other features planned for the caching tool include edge-side includes, using Twig for templating and statistics recorded to a database.

Mike Wallner has shared a quick and easy HTTP caching technique in a new post to his blog today. The key is in using the PEAR HTTP_Header package.

Ever watched youself browsing e.g. a web forum? Noticed that you viewed the same page several times? Well, this means extraordinary and useless load for your server if there's no caching mechanism implemented in the web application. Even if there is some file or db cache you can still improve performance with implementing some http cache.

With a few simple lines of code using HTTP_Header, you can tell your scripts how long to set the "expires" header to on your requests. This increment (in seconds) is relayed to the browser to tell it when to next fetch the page and not reload from cache.

In a new post to his blog Ulf Wendel has pointed out that the mysqlnd query cache plugin quickstart is posted on the docs.php.net site.

New in the PHP manual: a quickstart for the mysqlnd query cache plugin. PECL/mysqlnd_qc, the mysqlnd query cache plugin, is transparent and ease to use. But, how? Some pointers have been given in assorted presentations, here on my blog and in some, few examples from the manual. Fixed. You can now browse a quickstart to gain a quick overview.

The query cache plugin can replace the query caching MySQL does and can help with things like multiple storage options (memory, APC, Memcache, etc) and almost no changes to your application. There's also a method (mysqlnd_qc_get_query_trace_log) that comes with the plugin that gives you a "stack trace" of every query run through the MySQL interface.

Dave Marshall has a new post to his blog showing one method for defending against cache stampedes from assaulting your caching servers and (possibly) bringing them down.

I've recently had a problem with a rather large operation (that could probably be optimised considerably, but nevermind), where by if the cached result of the operation expired, several web server threads would attempt the operation, causing some major headaches for our database and web servers. This is something I've come across before, and is commonly(?) known as a Cache Stampede. This is bad, this post describes the basics of what I've done to deal with it.

His example uses a Zend_Cache interface to Memecache, but it could be applied in other places too. His method uses a binary semaphore to check and see if there's a "lock" and sleep for a bit before checking again. Sample code is included showing how to create this system and how to refresh the data with a new expiration on a cache miss.

In a recent post to his blog Brian Swan takes a look at working with sessions in PHP and, specifically, how to save them to Azure along with all of their data.

In my last post, I looked at the session handling functionality that is built into the Windows Azure SDK for PHP, which uses Azure Tables or Azure Blobs for storing session data. As I wrote that post, I wondered how easy it would be to use SQL Azure to store session data, especially since using a database to store session data is a common and familiar practice when building distributed PHP applications. As I found out, using SQL Azure to store session data was relatively easy (as I'll show in this post), but I did run into a couple of small hurdles that might be worth taking note of.

He uses PHP's own session_set_save_handler to point to his custom Azure handling class with the needed methods (like write, close and destroy). He breaks it out into three simple steps, some with a bit of code attached:

• Create the database, table, and stored procedure
• Add the SqlAzureSessionHandler class to your project
• Instantiate SqlAzureSessionHandler before calling session functions as you normally would

The code for the Azure handling class can be downloaded here.

Sébastien Thomas has a recent post to his blog shows how (with just a bit of code) you can monitor your APC cache usage on your local host.

I won't go deep into how OpCode caches work, you will find a lot of docs, just google for APC, Xcache, eAccelerator... What I can say is that APC (as other caches do) will save binary parts of your PHP code into memory and use it when you call for the same PHP function again. This way you save all the PHP file opening, parsing, etc. [...] One thing you won't come accross often on internet is How (the hell) do I know if APC is performing well ?

His answer comes in the form of code based on the APC-PHP-Monitor script. He changed it slightly to allow for use in other places, like with Nagios monitoring. A Nagois template is included to query the cache and report back a hit ratio. An example of the full cache results can be seen here complete with general cache info, hits, misses and file versus user caching stats.

On PHPBuilder.com today Jason Gilmore has written up a new tutorial about using memcached distributed caching for better performance in your web applications.

You probably know one of the easiest ways to improve performance is by caching all or parts of a page. But what might not be so obvious is exactly how this is accomplished. As it happens, a great solution called Memcached makes it trivial to incorporate caching into your website with great effect. In fact, relied upon by some of the largest websites in the world, among them Facebook, Twitter, Zynga, and YouTube, Memcached has essentially become the de facto website caching solution!

He walks you through installing the memcache extension for PHP (from PECL) and includes a bit of sample code that caches some fetched MySQL results to to the memcache server. With the extension installed you're just a few simple function calls away from better performance.

Brian Swan has a new post to his blog today showing you how to use caching for performance tuning on your Windows/IIS PHP application. He uses the IIS 7 output caching method instead of an external cacing tool or library.

The IIS output caching module allows you to configure IIS to cache dynamic pages generated by PHP. When a PHP page becomes "hot", the content of the page is cached so that is served without executing the script that generates it. [...] With the IIS Output Caching module you can cache all pages generated by PHP, vary what is cached by query string parameter value, or vary what is cached by header value.

He touches briefly on when he thinks you should use output caching for your applications since it can add extra overhead if it's not actually needed. He suggests turning it on when you have entire pages that don't change often and could benefit from just being displayed as-is. He shows how to enable the caching on IIS and includes some bits of code to show the results. There's a few other handy features he points out too like a file change notification and a configuration for a time interval caching rule.

Michael Nitschinger has put together a guide to caching responses in the Lithium framework - a simple update that means your application dosen't even need to reach the controllers to do its job.

I've hacked together a small example on how to easily cache full responses in Lithium. If you need to cache full Response objects in Lithium (which means that your controllers don't even get called when there's a cache hit), you can place this in your app/config/bootstrap/cache.php file (note that this is certainly not "production ready", but it should give you a starting point).

The code adds a new filter to run on execute that takes the current object (the Response object hit the first time) and use the Cache functionality to push it into storage. Their cache key is based on the URL, so each requests is cached individually. You can find out more about filters and the framework at Lithify.me.