Wordpress - Using pre_get_posts with WP_Query
The simplest way is to add the action right before the query and remove it immediately after.
add_action('pre_get_posts', 'some_function_in_functionsphp');
$my_secondary_loop = new WP_Query(...);
remove_action('pre_get_posts', 'some_function_in_functionsphp');
if( $my_secondary_loop->have_posts() ):
while( $my_secondary_loop->have_posts() ): $my_secondary_loop->the_post();
//The secondary loop
endwhile;
endif;
wp_reset_postdata();
EDIT
Another technique you can use is to set your own query var and check for that in a hook:
// tell WordPress about our new query var
function wpse52480_query_vars( $query_vars ){
$query_vars[] = 'my_special_query';
return $query_vars;
}
add_filter( 'query_vars', 'wpse52480_query_vars' );
// check if our query var is set in any query
function wpse52480_pre_get_posts( $query ){
if( isset( $query->query_vars['my_special_query'] ) )
// do special stuff
return $query;
}
add_action( 'pre_get_posts', 'wpse52480_pre_get_posts' );
and in the template:
// set the query var (along with whatever others) to trigger the filter
$args = array(
'my_special_query' => true
);
$my_secondary_loop = new WP_Query( $args );
pre_get_posts
fires for every post query:
- get_posts()
- new WP_Query()
- That random recent posts widget your client installed without you knowing.
- Everything
-- @nacin
With that being said unless you exclude your filter use the conditional: is_main_query()
then your filter will fire on your new WP_Query.
If you only want to target your specific new WP_Query then there is no way to do that.