Pass Contao filter/search/order settings to your export class

myExportClass.php

<?php 

/**
 * Class MyExport
 */
class MyExport
{

    /**
     * @param \DataContainer $dc
     *
     * @return \Model\Collection|null|static
     */
    public function getRecords(\DataContainer $dc)
    {
        // Get all filter/search/sorting settings from the session
        $filter = $dc->Session->get('filter')[$dc->table];
        $search = $dc->Session->get('search')[$dc->table];
        $sorting = $dc->Session->get('sorting')[$dc->table];

        // I don't need any limit settings
        unset($filter['limit']);

        $i         = 0;
        $arrFields = array();
        $arrOptions =array();

        // add filter settings
        if (is_array($filter)) {
            foreach ($filter as $k => $v) {
                $arrFields[0][$i] = $dc->table . '.' . $k . '=?';
                $arrFields[1][$i] = $v;
                $i++;
            }
        }

        // add search settings
        if (!empty($search['value'])) {
            $arrFields[0][$i] = 'LOWER(CAST(' . $dc->table . '.' . $search['field'] . ' AS CHAR)) REGEXP LOWER(?)';
            $arrFields[1][$i] = $search['value'];

            // alternative: get german umlauts, fe. ä from a
            // $arrFields[0][$i] = $dc->table . '.' . $search['field'] . ' LIKE ?';
            // $arrFields[1][$i] = '%' . $search['value'] . '%';
        }

        // add order settings
        $arrOptions['order'] = (!empty($sorting)) ?  $sorting : 'id ASC';

        // fetch data / replace MyModel!
        if (!empty($arrFields)) {
            $objExport = MyModel::findBy(array_values($arrFields[0]), array_values($arrFields[1]), $arrOptions);
        } else {
            $objExport = MyModel::findAll($arrOptions);
        }

        return $objExport;
    }
    
    
     /**
     * @param \DataContainer $dc
     *
     * @return string
     */
    public function export(\DataContainer $dc)
    {

        $objExport = $this->getRecords($dc);
        
        // get your data, fe. $objExport->id
        dump($objExport);
    }
}