WordPress Query Multisite

This is a custom version of WP_Query_Multisite, by ericandrewlewis, to support multisite post queries but without changing the class declaration, we will use the good ol' WP_Query. Just by entering the custom query var multisite => true on your query args and your query is now global.

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Example usage

$query = new WP_Query( [ 'multisite' => true ] );

while($query->have_posts()) {
    $query->the_post();
    
    switch_to_blog( $post->site_ID );
        
    echo $blog_id . get_the_title() . '<br>';
        
    restore_current_blog();
}

wp_reset_postdata();

To modify what sites are queried, create a 'sites' element in the $args in the constructor parameter, with a sub-element of either 'sites__in' or 'sites__not_in', which will be an array similar to 'posts__in' in the WP_Query object.

$args = [
    'multisite' => 1,
    'sites__in' => [ 1, 2, 3, 5 ]
];
$query = new WP_Query( $args );

while($query->have_posts()) {
    $query->the_post();
    
    switch_to_blog( $post->site_ID );
    
    echo $blog_id . get_the_title() . '<br>';
    
    restore_current_blog();
}

wp_reset_postdata();

Automatic multisite search example

On your functions.php:

add_action('pre_get_posts', function ($query) {

    if( !is_admin() && $query->is_main_query() && $query->is_search() ) {
        $query->set('multisite', true);
    }
    
});