你应该可以从相同的$wp_query 对象：

global $wp_query;
$num_pages = $wp_query->found_posts;

如果您只是想得到一个可以显示的字符串，那么这个修改后的函数版本就可以了。

function get_post_number()
{
    global $wp_query;

    /*
     * Get current page number. Set page 1 to one as get_query_var( \'paged\' ) will be 0
     */
    $current_page_number   = get_query_var( \'paged\' ) ? get_query_var( \'paged\' ) : 1;
    /* 
     * Get the posts_per_page option that is set under "Reading"
     */
    $posts_per_page        = get_option( \'posts_per_page\' );
    /*
     * Get the current post position in the loop, add 1 because the counter starts at 0
     */
    $current_post_position = $wp_query->current_post + 1;

    /*
     * If this is page one, return the post position as is
     */
    if ( $current_page_number == 1 )
        return $current_post_position;

    /*
     * Calculate the post number on paged pages
     */
    return ( ( $posts_per_page * ( $current_page_number - 1 ) ) + $current_post_position ). \'/\' . $wp_query->found_posts;
}