WordPress pre_get_posts: Customize the Query Parameter of WP_Query – WordPress Tutorial

WordPress pre_get_posts hook allows us to change the query parameter of WP_Query before starting query posts. In this tutorial, we will introduce how to use it.

How to use pre_get_posts?

You can use this hook as follows:

add_action( 'pre_get_posts', 'pre_get_posts_function' );

You should implement pre_get_posts_function by your own.

How to implement pre_get_posts_function?

Here is an example:

function pre_get_posts_function( $query ){
    $query->set( 'post_type', array( 
			'post',
			'course'
		) );
    return $query;
}

This function will receive a $query parameter, which contains the sql condition that will be used in WP_Query.

We can use $query->set() function to change the query condition of WP_Query. In order to set query parameters correctly, you should know what query parameters will be used in WP_Query. Here is an tutorial:

A Full List of WordPress WP_Query Query Arguments ($args) – WordPress Tutorial

As to example code above, we will set post_type query parameter to “post” and “course“, which means we will query two types of posts.

We also can set different query parameters by conditions, here is an example:

function pre_get_posts_function( $query ){
    if (is_admin() || !$query->is_main_query()){
        return;
    }
    if ($query->is_search() ) {
        $query->set('posts_per_page', 30);
    }
    if($query->is_main_query() && !is_admin() && $query->is_home()) {
	$query->set( 'cat', '-4' );
    }
    return $query;
}

We can use $query->is_function() to check different conditions.