$row_count = mysql_result(mysql_query("SELECT COUNT(*) FROM modx_catalog WHERE (`category`='" . mysql_real_escape_string($row['category']) . "');"), 0);
$query = array();
while (count($query) <= 4) {
    $query[] = "(SELECT * FROM modx_catalog WHERE (`category`='" . mysql_real_escape_string($row['category']) . "') LIMIT ".rand(0, $row_count).", 1)";
}
$query = implode(' UNION ', $query);
$result = mysql_query($query);
while ($rw = $this->modx->db->getRow($result)):
    if ($this->snippet_mode) 
        $rw['link'] = $this->Link(array('rowid'=>$rw['id']));
    $this->rws[] = $rw;
endwhile;
foreach($this->rws as $rw):
$url='<a href="'.$rw['link'].'" title="подробнее о товаре" target="_blank">'.$rw['name'].'</a><br>';
$var=str_replace("0?","product?",$url);
echo $var;
endforeach;