Snippet for MiniShop2. Get vendors from category.

msVendors.php

<?php
$pdo = $modx->getService('pdoTools');

$fieldName =  $modx->getOption('fieldName', $scriptProperties, 'vendor');
$fieldClass = $modx->getOption('fieldClass', $scriptProperties, '');
$firstOption = $modx->getOption('firstOption', $scriptProperties, '');
$parent =  $modx->getOption('parent', $scriptProperties, 0);
$depth = $modx->getOption('depth', $scriptProperties, 10);
$limit = $modx->getOption('limit', $scriptProperties, 100);
$tplOuter = $modx->getOption('tplOuter', $scriptProperties, '@INLINE <select name="[[+name]]" class="[[+class]]">[[+rows]]</select>');
$tplRow = $modx->getOption('tplRow', $scriptProperties, '@INLINE <option value="[[+id]]">[[+name]]</option>');

$q = $modx->newQuery('msProduct');
$q->innerJoin('msProductData', 'Data', 'msProduct.id = Data.id');
$q->innerJoin('msVendor', 'Vendor', 'Data.vendor = Vendor.id');
$q->leftJoin('msCategoryMember', 'Member', 'Member.product_id = msProduct.id');
$q->select('Vendor.id, Vendor.name');
$q->groupby('Vendor.id');
$q->sortby('Vendor.name');
$q->limit($limit);

$parents = $modx->getChildIds($parent, $depth);
$parents[] = $parent;

$q->where(array('msProduct.parent:IN' => $parents));
$q->orCondition(array('Member.category_id:IN' => $parents));

$options = '';

if (!empty($firstOption)) {
	$options .= $pdo->getChunk($tplRow, array(
		'id'   => '',
		'name' => $firstOption
	));
}

if ($q->prepare() && $q->stmt->execute()) {
	while ($row = $q->stmt->fetch(PDO::FETCH_ASSOC)) {
		$options .= $pdo->getChunk($tplRow, $row);
	}
}

$output = $pdo->getChunk($tplOuter, array(
	'name' => $fieldName,
	'class' => $fieldClass,
	'rows' => $options,
));
 
return $output;