groups_to_access_options.php

<?php

elgg_register_event_handler('init', 'system', 'my_init');

function my_init () {
    elgg_register_plugin_hook_handler('access:collections:write', 'all', 'my_acl_options');
}

/**
 * Allow selecting any group as read/write access regardless of page context
 * 
 * By default read/write access to group content can be set only for the group
 * that is container of the content. This handler allows acl to be set as any
 * group even when creating content outside groups.
 * 
 * @param string $hook   'access:collections:write'
 * @param string $type   'user'
 * @param array  $return Array of "Acl id => Acl name" pairs 
 * @param array  $param  Array with user_id and site_id
 * @return array $return
 */
function my_acl_options($hook, $type, $return, $params) {
	$user_guid = $params['user_id'];
	$user = get_entity($user_guid);
	if (!$user) {
		return $return;
	}

	$groups = elgg_get_entities_from_relationship(array(
		'type' => 'group',
		'relationship' => 'member',
		'relationship_guid' => $user_guid,
		'inverse_relationship' => FALSE,
		'limit' => false,
	));

	if ($groups) {
		foreach ($groups as $group) {
			$return[$group->group_acl] = elgg_echo('groups:group') . ': ' . $group->name;
		}
	}

	return $return;
}