MODX Snippet to get a field from a resource based on a supplied resource id, meant to be used as an output filter.

toResourceField.snippet.php

<?php
/**
 * Gets a field from a resource based on a supplied resource id, meant to be used as an output filter.
 *
 * Based on a resource ID a field can be retrieved. This can be standard fields as 'pagetitle' or 'alias',
 *  but a few custom fields are also available; 'siblingNextId', 'childrenFirstId', and 'childrenCount'.
 * Only resources that are not marked as 'deleted' or 'hidemenu', and that is marked as 'published' are returned.
 * Examples:
 * [[*id:toResourceField]] => returns the resource pagetitle
 * [[*id:toResourceField=`alias`]] => returns the resource alias
 * [[*id:toResourceField=`childrenFirstId`]] => returns the ID of the first child of the resource.
 *                                                 If the resource has no children, the resource ID is returned
 * [[*id:toResourceField=`childrenCount`]] => returns the number of children for the resource
 * [[*id:toResourceField=`siblingNextId`]] => returns the ID of the next sibling of the resource.
 *                                            If the resource has no 'next' sibling, it returns the first child of the parents next sibling.
 *                                            If the parent has no 'next' sibling, it returns the grandparent.
 * As snippet:
 * [[toResourceField? &input=`[[*id]]` &options=`alias`]]
 *
 * @author Jacob Flygenring <jacob@bettercollective.com>
 * @since 2013-05-27
 *
 * @param int $input The resource id to get the field from.
 * @param string $options The name of the field to get. Defaults to 'pagetitle'.
 *
 * @return (int|string) The value of the chosen field in the given resource.
 */

if(!function_exists('siblingNextId')) {
    function siblingNextId($intResourceId) {

        global $modx;
        list($intParentId) = $modx->getParentIds($intResourceId, 1);
        $objResource = $modx->getObject('modResource', $intResourceId);
        $intMenuIndex = $objResource->get('menuindex');
        $arrCriteria = array(
            'parent'      => $intParentId
            , 'deleted'   => false
            , 'hidemenu'  => false
            , 'published' => true
            , 'menuindex' => ($intMenuIndex + 1)
        );
        $objXpdoQuery = $modx->newQuery('modResource');
        $objXpdoQuery->where($arrCriteria);
        $objXpdoQuery->limit(1);
        $objResource = $modx->getObject('modResource', $objXpdoQuery);

        if(null != $objResource) {
            $intReturn = $objResource->get('id');
        }
        else {
            $intReturn = 0;
        }

        return $intReturn;
    }
}

if(!function_exists('childrenFirstId')) {
    function childrenFirstId($intResourceId) {

        global $modx;
        $arrCriteria = array(
            'parent'      => $intResourceId
            , 'deleted'   => false
            , 'hidemenu'  => false
            , 'published' => true
        );
        $objXpdoQuery = $modx->newQuery('modResource');
        $objXpdoQuery->where($arrCriteria);
        $objXpdoQuery->sortby('menuindex', 'ASC');
        $objXpdoQuery->limit(1);
        $objResource = $modx->getObject('modResource', $objXpdoQuery);

        if(null != $objResource) {
            $intReturn = $objResource->get('id');
        }
        else {
            $intReturn = $intResourceId;
        }

        return $intReturn;

    }
}

if(!function_exists('childrenCount')) {
    function childrenCount($intResourceId) {

        global $modx;
        $arrCriteria = array(
            'parent'      => $intResourceId
            , 'deleted'   => false
            , 'hidemenu'  => false
            , 'published' => true,
        );

        return $modx->getCount('modResource', $arrCriteria);

    }
}


$intResourceId = isset($input) ? (int)$input : 0;
if($intResourceId > 0) {

    $strField = (strlen($options) > 0) ? $options : 'pagetitle';

    switch($strField) {
        case 'siblingNextId':
            $intMaxLevels = 2;
            $intCurrentLevel = $intMaxLevels;
            do {
                $mixReturn = siblingNextId($intResourceId);

                if(0 == $mixReturn) {
                    list($intResourceId) = $modx->getParentIds($intResourceId, 1);
                    $intCurrentLevel -= 1;
                }
            }
            while(0 == $mixReturn && $intCurrentLevel > 0);

            if($intCurrentLevel != $intMaxLevels) {
                // A next sibling wasn't found, but a parents next sibling was, so just get first child from that parent
                if($mixReturn > 0) {
                    $mixReturn = childrenFirstId($mixReturn);
                }
                // Neither a next sibling or a parents next sibling was found, so return grand parent
                else {
                    $mixReturn = $intResourceId;
                }
            }
            break;

        case 'childrenFirstId':
            $mixReturn = childrenFirstId($intResourceId);
            break;

        case 'childrenCount':
            $mixReturn = childrenCount($intResourceId);
            break;

        default:
            $objResource = $modx->getObject('modResource', $intResourceId);
            $mixReturn = $objResource->get($strField);
            break;
    }

    return $mixReturn;
}