[Plugin: Posts 2 Posts] function to display related posts on frontend?

1. How to assign an array of objects to a type.
— say there were multiple actors in the movie, and I want to display them all. yeah, I know, bad example but I think it gets the point across

See this topic: [Plugin: Posts 2 Posts] More than one related post.

2. How to assign an array of post types to another type.
— say I want to not only have actors type assigned to the movie, but directors as well.

p2p_register_connection_type('movie', 'actor');
p2p_register_connection_type('movie', 'director');

I will probably make it accept an array as the second argument too.

Displaying conencted posts:

The most flexible way to display related posts is through a custom loop:

$connected_posts_ids = p2p_get_connected('to', get_the_ID(), 'actor');

query_posts(array('post__in' => $connected_posts_ids));
while ( have_posts() ) : the_post();

    the_title();

    // etc.

endwhile;
wp_reset_query();

The first argument is either ‘to’ or ‘from’.

I was not getting anything returned using a ‘to’ argument, when querying actor from the movies single page. I do have an actor chosen in the ‘connections’ dropdown, so that part seems to work.
When I run a print_r of $connected_posts_ids I get the following returned:

Array ( [0] => 78 )

must be missing something simple, as the function seems correct.

Yes, it’s supposed to return an array of related post ids. You then use that id list in query_posts(), as demonstrated above.

This one has me stumped, here is the code I am trying:

<?php
$connected_posts_ids = p2p_get_connected('from', get_the_ID(), 'artists');
print_r($connected_posts_ids);
query_posts(array('post__in' => $connected_posts_ids));
$testing = query_posts(array('post__in' => $connected_posts_ids));
print_r($testing);
while ( have_posts() ) : the_post();
echo get_post_meta(get_the_ID(), 'artistsimage', true);
    the_title();

    // etc.

endwhile;
wp_reset_query();
?>

the first part works:
print_r($connected_posts_ids);
That returns Array ( [0] => 78 )

However
print_r($testing);
returns Array ()
That is obviously the root of my problem as to why my artistsimage and title are not showing up.

What I don’t understand is where the array is ‘loosing’ it’s information between the first line and the second line of code.

huge props to a friend who figured this out for me. Posting here, because I am SURE that others will have this issue someday.

<?php
$connected_posts_ids = p2p_get_connected('from', get_the_ID(), 'artists');
query_posts(array('post__in' => $connected_posts_ids,'post_type'=>'artists'));
while ( have_posts() ) : the_post();
    the_title();
?>
<img src="<?php echo get_post_meta(get_the_ID(), 'artistsimage', true);?>">
<?php
    // etc.

endwhile;
wp_reset_query();
?>

the KEY was changing this one line:
$connected_posts_ids,'post_type'=>'artists'));

notice the post_type in there… otherwise it returns an empty set.

sure hope this helps someone else out.

With the development version (0.2-alpha), you can do this:

function my_p2p_callback($query) {
	while ( $query->have_posts() ) : $query->the_post();
		the_title();

		// etc.
	endwhile;
}

... later ...

p2p_list_connected('artist', 'to', get_the_ID(), 'my_p2p_callback');

p2p_list_connected() takes care of getting the correct posts and sends a WP_Query object to the callback.

To simply output an unordered list of post titles, do:

p2p_list_connected('artist', 'to');

Now that is so nice to have. After playing with post-to-post all day yesterday, I can see how this is going to become one of the favorite development plugins out there. Add in the taxonomy-metadata plugin, and I’m having a hard time finding any missing pieces for my projects.

Thank you very much!

Just thought I’d list generically what I did with the latest version of the plug-in after wandering around and looking at what other people have done. Thought I’d post in-case anyone else wanders upon this thread like I have…

global $post;

$sc_query = new WP_Query( array(
  'suppress_filters' => false,
  'post_type' => 'artist',
  'connected' => $post->ID) );

if($sc_query->have_posts()) :

echo '<ul>';

while($sc_query->have_posts()):$sc_query->the_post();
$sc_output ='';
$sc_output .= '<li><a href="' . get_permalink($post->ID) . '">';
$sc_output .= $post->post_title;
$sc_output .= '</a></li>';

echo $sc_output;

endwhile;

echo '</ul>';

endif;