get_page_children() not returning all child pages

Question

I have in my Wordpress theme, a section where I am getting child pages to display their information. This is what I have right now:

<?php 
                $my_wp_query = new WP_Query();
                $all_wp_pages = $my_wp_query->query(array('post_type' => 'page'));

                $staff = get_page_children(8, $all_wp_pages);

                foreach($staff as $s){
                    $page = $s->ID;
                    $page_data = get_page($page);
                    $content = $page_data->post_content;
                    $content = apply_filters('the_content',$content);
                    $content = str_replace(']]>', ']]>', $content);
                    echo '<div class="row-fluid"><span class="span4">'; 
                    echo get_the_post_thumbnail( $page ); 
                    echo '</span><span class="span8">'.$content.'</span></div>';
                } 
        ?>

I have five child pages that should be showing up, but only three are returning. I used print_r on $staff to see if the other pages were even in the array, but they aren't. I'm not sure what the problem could be.

Answer 1

There is nothing wrong with get_page_children() or new WP_Query(). By default WP_Query returns only the last x number of pages created. It's the limit imposed on WP_Query.

get_page_children() simply takes the pages array returned by WP_Query and filters the children pages from that list. According to WordPress Codex: get_page_children "...does not make any SQL queries to get the children."

To fix the issue simply use:

    $query = new WP_Query( 'posts_per_page=-1' );

Your code with the fix:

    <?php 
    $my_wp_query = new WP_Query();
    $all_wp_pages = $my_wp_query->query(array('post_type' => 'page', 'posts_per_page' => -1));

    $staff = get_page_children(8, $all_wp_pages);

    foreach($staff as $s){
        $page = $s->ID;
        $page_data = get_page($page);
        $content = $page_data->post_content;
        $content = apply_filters('the_content',$content);
        $content = str_replace(']]>', ']]>', $content);
        echo '<div class="row-fluid"><span class="span4">'; 
        echo get_the_post_thumbnail( $page ); 
        echo '</span><span class="span8">'.$content.'</span></div>';
    } 
    ?>

Here is a helper function that you can call whenever you need to get page children

    function my_get_page_children( $page_id, $post_type = 'page' ) {
        // Set up the objects needed
        $custom_wp_query = new WP_Query();
        $all_wp_pages    = $custom_wp_query->query( array( 'post_type' => $post_type, 'posts_per_page' => -1 ) );

        // Filter through all pages and find specified page's children
        $page_children = get_page_children( $page_id, $all_wp_pages );

        return $page_children;
    }

Example

You code with with the helper function

    foreach(my_get_page_children(8) as $s){
        $page = $s->ID;
        $page_data = get_page($page);
        $content = $page_data->post_content;
        $content = apply_filters('the_content',$content);
        $content = str_replace(']]>', ']]>', $content);
        echo '<div class="row-fluid"><span class="span4">'; 
        echo get_the_post_thumbnail( $page ); 
        echo '</span><span class="span8">'.$content.'</span></div>';
    } 

Answer 2

I've had a similar problem - looks like get_page_children behaves weird... (in my case, for one page which had three children it returned three, for another with four it returned zero! - can't work it out..)

I got round it by using a custom query instead:

$params = array(
'post_type'=>'page',
'post_parent'=> 8,
);
$staff = query_posts($params);

Similar here: http://www.sanraul.com/2010/08/28/get-page-children/

NOTE: depending on where you use this, you might need a wp_reset_query(); as well - or else that query_posts() could break your main loop!

Hope that helps! - A