Getting content from a single *page* of a post

Question

What function can I use to fetch content of a single page within a post? Let's say I want to split my post into 5 pages - how can I get content of, say, page 3?

Can't seem to find this in Codex...

Answer 1

This should do the trick:

/**
 * For posts paginated using <!--nextpage-->, return a particular "page" of content.
 * This function uses code from WP's setup_postdata() function.
 * @param string $content the content to search for paginated page content.
 * @param int $page_number the index of the page to return the content for.
 */
function get_nextpage_content( $content, $page_number ) {
    if ( strpos( $content, '<!--nextpage-->' ) ) {
        $content = str_replace("\n<!--nextpage-->\n", '<!--nextpage-->', $content);
        $content = str_replace("\n<!--nextpage-->", '<!--nextpage-->', $content);
        $content = str_replace("<!--nextpage-->\n", '<!--nextpage-->', $content);
        $pages = explode('<!--nextpage-->', $content);
        return ( isset ( $pages[$page_number - 1] ) ) ? $pages[$page_number - 1] : false;
    } else {
        return false;
    }
}

Usage:

// Get the second page of content with a paginated post
echo apply_filters( 'the_content', get_nextpage_content( $post->post_content, 2 ) );

Answer 2

You should first explode the content, and then perform a few functions on the content to enable WordPress' "Auto paragraph" formatting and Shortcodes.

$post_content = $wpdb->get_var("SELECT post_content FROM $wpdb->posts WHERE ID = {$post->ID} LIMIT 0,1");
$raw_pages = explode('<!--nextpage-->', $post_content);
foreach($raw_pages as $raw_page){
    $pages[] = wpautop( do_shortcode( trim($main_content) ) );
}

Now you can echo each page like so:

<?php echo $page[0]; // Page 1 ?>

You can also implement this feature/concept a tad differently. I like to split my post into two pages to give my copywriter the ability to create the main content and sidebar content. I basically assign the second page to the sidebar. While you could use the same code as above, a cleaner (yet less flexible way) might be to do something like this...

$post_content = $wpdb->get_var("SELECT post_content FROM $wpdb->posts WHERE ID = {$post->ID} LIMIT 0,1");
list($main_content, $sidebar_content) = explode('<!--nextpage-->', $post_content);
$main_content = wpautop( do_shortcode( trim($main_content) ) );
$sidebar_content = wpautop( do_shortcode( trim($sidebar_content ) ) );

Now I can just echo out either the $main_content or $sidebar_content variable wherever I want in my page template.