$highestColumn = $sheet->getHighestColumn(); // 取得总列数
++$highestColumn;

for ($row = 5; $row <= $highestRow; $row++) {
    $rowData = array();
    for ($column = 'A'; $column != $highestColumn; $column++) {
        $columnData = $sheet->getCell($column . $row)->getValue();
    }        
}
两处改动:1、++$highestColumn;2、$column != $highestColumn;