Sorting by custom fields with the posts_orderby filter

Unless you use ‘meta_key=my_meta_key’ in your query, you must use a JOIN filter to join the postmeta table so the meta_key/value will be available for the orderby filter.

Check this article for more:

http://wordpress.mcdspot.com/2010/05/30/filters-to-modify-a-query/

Hey guys,

Picking up this thread. Hopefully someone will be able to help.

Here’s my query:

$args = array(
	'post_type'      => array( 'projects', 'post' ),
	'posts_per_page' => -1,
	'post_status' => 'publish'
	'orderby'     => 'meta_value',
	'order'       => 'DESC',
	'meta_key'    => 'code'
);

$projects = new WP_Query( $args );

My problem is the posts don’t have the meta_key of code so they won’t appear in my loop. I’m thinking that I can use the posts_orderby filter along with a couple other filters to get the job done. Only problem, I can’t figure out how to setup the filters. Any help?

Many thanks,
Jacob

Thanks vtxyzzy,

I really appreciate your response!

Here’s what I’ve done:

in my front-page template:

$args = array(
	'post_type'      => array( 'projects', 'post' ),
	'posts_per_page' => -1,
	'post_status' => 'publish'
);
		$mam_global_fields  = ', IFNULL(pm.meta_value,0) AS sort_key';
		$mam_global_join    = " LEFT JOIN $wpdb->postmeta pm ON (pm.post_id = $wpdb->posts.ID AND pm.meta_key = 'code')";
		$mam_global_orderby = 'sort_key DESC';

$projects = new WP_Query( $args );

In my functions.php:

function mam_posts_fields($fields) {
   global $mam_global_fields;
   if ( $mam_global_fields ) {
		$fields .= ( preg_match('/^(\s+)?,/', $mam_global_fields) ) ? $mam_global_fields : ", $mam_global_fields";
	}
   return ( $fields ) ? $fields : '';
}

function mam_posts_join($join) {
   global $mam_global_join;
   if ( $mam_global_join && $join ) {
		$join .= ' ' . $mam_global_join;
	}
   return ( $join ) ? $join : '';
}

function mam_posts_orderby($orderby) {
   global $mam_global_orderby;
   if ( $mam_global_orderby && $orderby ) {
		$orderby = $mam_global_orderby;
	}
   return ( $orderby ) ? $orderby : '';
}

add_filter( 'posts_fields',  'mam_posts_fields'  );
add_filter( 'posts_join',    'mam_posts_join'    );
add_filter( 'posts_orderby', 'mam_posts_orderby' );

When I load the page, I get an error:

Parse error: syntax error, unexpected T_VARIABLE in …/wp-content/themes/ncm/functions.php on line 246

Which is this variable: global $mam_global_fields;

Can’t find any syntax errors, but no matter what I do, I can’t get the page to load with this code. Any ideas?

Thanks again,
Jacob

You’re quick! Much appreciated.

http://pastebin.com/327Pvcj2

When I remove the new code, everything works fine.

Thanks again for your help. This topic has eluded me for some time.

-J

I cleaned out a bunch of commented functions that I use on some sites. It’s kind of a catch all functions.php that I use on all my sites. Would you like me to repost with all of the commented code?

-J

I’ll give it a try right now. Did you update to 3.4, yet?