gogocarto-category-filter.php

<?php
foreach($data as $key => $row) {
    $categories = array($row['Category']);
    foreach($row as $h => $v) {
        if (substr($h, 0, 3) == 'pr:') {
            $cat = substr($h, 3);
            if ($v != '') {
                $categories[] = $cat;
            }
            unset($data[$key][$h]);
        }
    }
    $data[$key]['Category'] = join(',', $categories);
}