Get article by name or number

English forums
,
5

class oxGetArticleByNumberPlugin extends oxErpPluginBase
{
public function invoke($aParams)
{
$am = $this->getConfig()->getParameter(‘am’);
$art = $this->getConfig()->getParameter(‘oxartnum’);
$aResult = array();

    		$rs = oxDb::getDB()->select( "SELECT OXID FROM ...");	
    		
            if ($rs != false && $rs->count() > 0)
     {
                while (!$rs->EOF) {
                    $rs->fields = array_change_key_case($rs->fields, CASE_LOWER);
                    $aResult[] =  $rs->fields['oxid']; //only the oxid
                    $rs->fetchRow();
     }

    		
        $oResult = new oxERPReturn();
        $oResult->aResult = $aResult;
        $oResult->blResult = true;
        return $oResult;
}

}
Call to undefined method oxGetArticleByNumberPlugin::getConfig().

but when I try:
$am = $aParams[‘am’];
$art = $aParams[‘oxartnum’];
there is no error but $art param is empty.