对于数量相对较少的帖子，您可以尝试以下方法：

/**
 * Return a single random search result
 */
add_action( \'pre_get_posts\', function( \\WP_Query $q )
{
    if( ! is_admin() && $q->is_main_query() && $q->is_search() )
    {
        $q->set( \'posts_per_page\', 1 );
        $q->set( \'orderby\', \'rand\' );
    }
} );

请注意，随机排序不能很好地扩展

另一种方法是从搜索查询中获取最多15篇帖子，按随机顺序排列这些帖子，然后显示单个帖子：

/**
 * Return max 15 posts from the search results, ignore paging
 * and then only display a single random post
 */
add_action( \'pre_get_posts\', function( \\WP_Query $q )
{
    if( ! is_admin() && $q->is_main_query() && $q->is_search() )
    {
        $q->set( \'posts_per_page\', 15 );
        $q->set( \'no_found_rows\', true ); // ignore paging

        // Display only a single random post from these 15
        add_filter( \'the_posts\', \'wpse_random_post\' );
    }
} );

/**
 * Return a single random post from the posts results array.
 */
function wpse_random_post( Array $posts )
{
    remove_filter( current_filter(), __FUNCTION__ );

    if( count( $posts ) > 0  )
        $posts = [ $posts[array_rand( $posts )] ];

    return $posts;
}