<?php
    private function _distinct_pr_years() {
        $ID = $this->ID;
        $q         = new SQLQuery();
        $q->select = array('DISTINCT YEAR(Date) SQLYear');
        $q->from   = array("PressRelease LEFT JOIN SiteTree_Live ST ON PressRelease.ID = ST.ID");
        $q->where  = array("ST.ParentID = {$this->ID}");
        $q->orderby = "Date DESC";
        return $q->execute();
    }

    function PRYears() {
        $data  = new DataObjectSet();
        foreach ( $this->_distinct_pr_years() as $year ) {
            $data->push(
                new ArrayData(
                    array( 'Year' => $year['SQLYear'], 'Link' => $this->Link() . 'showyear/' . $year['SQLYear'] )
                )
            );
        }
        return $data;
    }