Many actions in WordPress will fire multiple times, which can lead to performance drags and undesired/intuitiveness results. Pippin Williamson points out that you can check how many times an action has already run, and modify your code to respond accordingly.
Normally any kind of global values that don’t change within a program’s execution should be defined as constants, but text domains within internationalized WordPress plugins are an exception to that rule. Mark Jaquith explains why it’s important to use a string instead.
I’ll be giving a presentation on building Child Themes at the Seattle WordPress Developer’s Meetup tomorrow. You can follow along with the presentation if you plan on attending.
BackPress is a useful project that packages the re-usable code from WordPress into an independent library you can use in non-WordPress projects.
Nathan Ingram put together a thorough post on backing up WordPress and a chart comparing various plugins and services.
Dave Clements has a great suggestion for adding snippets to a WordPress site in a way that will preserve them between theme changes: create a simple functionality plugin.
TJ Stein gave a really good presentation at WordCamp Chicago 2011 about scaling and performance issues with WordPress installations. He focuses a lot on using ngnix instead of Apache, but also covers PHP object caching, Varnish, CDNs, benchmarking, etc. It’s a good overview of current practices, but there’s also a lot of specific tips throughout.
This WordPress Answers page explains the differences between the query_post() and get_posts() functions, and their relation to the WP_Query class. They both use WP_Query internally, but should be used in different contexts. Using them in the wrong context could lead to bugs that are hard to track down.
Mark Maunder benchmarked several performance tuning measures with a WordPress installation on a VPS server to show which are most effective. The biggest improvements were from installing PHP-APC, setting up Nginx to proxy concurrent connections for Apache, and using MySQL’s query cache.
I wrote a new WordPress plugin for a side project and just released it into the repository. It creates a custom post type for markers and then inserts them into an embedded Google Map, using the post’s featured image as the map icon.
Note: all support requests should be posted to the support forums.