recorrer las celdas de una fila en excel

$row = $sheet->getRowIterator($fila)->current();
$cellIterator = $row->getCellIterator();
$cellIterator->setIterateOnlyExistingCells(FALSE); // This loops through all cells,
                                                  //    even if a cell value is not set.
                                                  // By default, only cells that have a value
                                                  //    set will be iterated.

foreach ($cellIterator as $cell) {
    $celda = $cell->getCoordinate();
}