public function export($id)
{
    $headers = array(
        "Content-type" => "text/csv",
        "Content-Disposition" => "attachment; filename=file.csv",
        "Pragma" => "no-cache",
        "Cache-Control" => "must-revalidate, post-check=0, pre-check=0",
        "Expires" => "0"
    );
 if (Repas::where('numsem', $id)->exists()) {
            $repasdelasem = Repas::where('numsem', $id)->first();
            $idsem = $repasdelasem->numsem;
            $repas = Repas::where('numsem', $idsem)->get();
    $columns = array('Jour', 'Date', 'Petit Dejeuner', 'Collation matin ', 'Dejeuner', 'Gouter', 'Diner');

    $callback = function() use ($repas, $columns)
    {
        $file = fopen('php://output', 'w');
        fputcsv($file, $columns);

        foreach($repas as $repasjour) {

            fputcsv($file, array($repasdujour->jour, $repasdujour->date, $repasdujour->petitdej, $repasdujour->colmat, $repasdujour->dejeune, $repasdujour->gouter, $repasdujour->diner ));
        }
        fclose($file);
    };
}
    return Response::stream($callback, 200, $headers);
}