Connection metadata

With Posts 2 Posts, it's possible to store arbitrary information per connection, i.e. to have connection metadata.

Defining editable fields

The fields a user can edit are defined via the 'fields' argument:

<?php
p2p_register_connection_type( array(
	'name' => 'posts_to_pages',
	'from' => 'post',
	'to' => 'page',
 
	'fields' => array(
		'count' => array(
			'title' => 'Count',
			'type' => 'text',
		),
		'role' => array( 
			'title' => 'Role',
			'type' => 'select',
			'values' => array( 'engineer', 'support', 'manager' )
		),
		'special' => array(
			'title' => 'Special',
			'type' => 'checkbox'
		),
		'colors' => array(
			'title' => 'Colors',
			'type' => 'checkbox',
			'values' => array( 
                                'green'=>__('Green','my-textdomain'), 
                                'yellow'=>__('Yellow','my-textdomain'), 
                                'blue'=>__('Blue','my-textdomain'), 
                                'white'=>__('White','my-textdomain') ),
			'default' => 'blue'
		),
	)
) );

Each connection in the box will now have four additional columns:

• a 'Count' column, with a simple text input.
• a 'Role' column, with a dropdown with 3 possible values: engineer, support, and manager.
• a 'Special' column, with a single checkbox.
• a 'Colors' column, with several checkboxes.

Dynamic default values

The 'default' key allows you to pre-fill a field with a static value. But what if you wanted for example to fill it with the excerpt of one of the posts? Instead of a static value, you can pass a callback:

<?php

p2p_register_connection_type( array(
	...

	'fields' => array(
		'blurb' => array(
			'title' => 'Post Blurb',
			'type' => 'textarea',
			'default_cb' => 'my_get_blurb',
		),
	)
) );

function my_get_blurb( $connection, $direction ) {
	global $post;

	$key = ( 'from' == $direction ) ? 'p2p_to' : 'p2p_from';

	$post = get_post( $connection->$key );
	setup_postdata( $post );

	return get_the_excerpt();
}

Accessing connection information

Ok, now you can input additional connection information, but how do you access it afterwards?

To display connection information, you use the connection id, which can be found in the $post variable as the p2p_id property:

<?php
while( $connected->have_posts() ) : $connected->the_post();
	echo '<li>';

	the_title();

	// Display count and type
	echo '<br>';
	echo 'Count: ' . p2p_get_meta( get_post()->p2p_id, 'count', true );
	echo '<br>';
	echo 'Type: ' . p2p_get_meta( get_post()->p2p_id, 'type', true );

	echo '</li>';
endwhile;

You might notice that p2p_get_meta() looks very similar to the get_post_meta() function. The only difference is that, instead of a post id, you're using a connection id.

Querying connections by their fields

Finally, it's also possible to filter connections depending on what metadata they have.

<?php
$connected = new WP_Query( array(
	'connected_type' => 'posts_to_pages',
	'connected_items' => get_queried_object(),
	'connected_meta' => array( 'type' => 'strong' )
) );

Or you could use the more advanced meta_query syntax:

<?php
$connected = new WP_Query( array(
	'connected_type' => 'posts_to_pages',
	'connected_items' => get_queried_object(),
	'connected_meta' => array(
		array(
			'key' => 'count',
			'value' => 5,
			'compare' => '>',
			'type' => 'numeric',
		)
	)
) );

This will get all connections which have the 'numeric' field value higher than 5.

Updating connection information

You can use p2p_add_meta(), p2p_update_meta() and p2p_delete_meta().