Understanding how to alter the main query and how to create custom queries in WordPress are two essentials for WordPress developers. You should familiarize yourself with a few things right away:
- What is the
WP_Queryclass, including creating new custom queries for secondary loops
- Never use
- Alter queries with the
You also need to watch WordPress Lead Developer Andrew Nacin talk about
WP_Query in depth in this WordPress.tv Presentation. Seriously, take notes. Follow the slides. Repeat parts multiple times. It might be the best hour you'll ever spend learning about WordPress.
Now, let me add a couple relatively unimportant points (in comparison) to the above resources on querying with WordPress.
You probably don't need
As Nacin points out in the video above,
wp_reset_query() unsets the main
$wp_query variable, then resets it to the value of
$wp_the_query, and then runs
wp_reset_postdata(). Well, if you're not using
query_posts(), then you really shouldn't be messing with the main
$wp_query variable, as
All you need to do after a custom
WP_Query is use
wp_reset_postdata(), which resets various global post variables to their original values.
$wp_query to store your custom query information
The other aggravating thing I see in a lot of custom
WP_Query instances, is people storing the main
$wp_query variable temporarily under a new name, and then using
$wp_query to store their custom query information, before resetting
$wp_query back to its original value at the end of the query. This is completely unnecessary and scary.
All it takes is one bad copy / paste for this to cause you many headaches. Please, for all that is good, just assign your custom query to its own variable. Just for fun, I often store mine as
$krogsquery, because I'm pretty sure that's not going to mess with anyone else's globals.
Here's a sample of these two previous items in a
WP_Query that's not setup properly:
I assume the reason people sometimes override the main query variable this way is because they think they need to in order to call items like
have_posts() and other conditionals. As Nacin points out in his talk, you have access to all of those as methods of your new
WP_Query already, and should call them that way (I actually am calling
have_posts() this way in the query above). And again as Nacin points out, those functions are just calling the methods of the main
WP_Query to start with.
WP_Query done right
So, here's a sample
WP_Query that you can utilize for your custom loops that uses a custom variable name and properly resets post data.
It's not the end of the world if you've been doing what I describe above. Not using
query_posts() is a good start toward improving your life as a WordPress developer. But these are a couple of common bits of code I see in custom loops out there that I thought I'd try and help us all do better on.
Seriously, have I mentioned you should watch Nacin's presentation?