The problem is that you're storing the hungarian formula directly in the cell.
You can work with hungarian formulae, but the formula stored in a cell and referenced by the calculation engine, and the writers
must be English, so you need to 'translate' before storing.
$hungarianFormula = '=SZUMHA(K:K;"' . $line["felelossegi_kor"] . '";E:E)';
$englishFormula = PHPExcel_Calculation::getInstance()->translateFormulaToEnglish($hungarianFormula);
$worksheet->setCellValueExplicitByColumnAndRow(2, $row, $englishFormula, PHPExcel_Cell_DataType::TYPE_FORMULA);
This is described in section 4.6.5 Locale Settings for Formulae of the developer documentation