PhpSpreadsheet输出加密文本，而不是开始下载

我正在用slimframework创建一个API，我有一个路径，我试图将数据导出到excel文件并下载它，而不是保存它，但当我尝试这样做时，它会输出如下文本

��ࡱ�;�，问题是我有三种获取数据的方法（不同的sql查询），但只有一种失败，有人能解释为什么吗

这是其中一个工作正常的阵列：

Array
(
       [0] => Array
          (
            [id_asistente] => 1
            [nombre] => adfadsfas
            [inst_procedencia] => sadfsa
            [perfil_academico] => asdfasdf
            [estado] => asdfsaf
            [correo] => mail@gmail.com
            [cursos_inscritos] => 1
        )

    [1] => Array
        (
            [id_asistente] => 2
            [nombre] => asdfsafsaf
            [inst_procedencia] => asdfasfsa
            [perfil_academico] => asdfasdfsdf
            [estado] => sdfdsafadfs
            [correo] => mailll@gmail.com
            [cursos_inscritos] => 1
        )

    [2] => Array
        (
            [id_asistente] => 3
            [nombre] => asdfasfsfa
            [inst_procedencia] => asdffds
            [perfil_academico] => asdfasdfdsaf
            [estado] => asdfasdf
            [correo] => edu@gmail.com
            [cursos_inscritos] => 0
        )

    )

这就是阵列，我不知道为什么，它不工作：

Array
(
[0] => Array
    (
        [id_asistente] => 2
        [nombre] => asdasdasdad
        [inst_procedencia] => Asda
        [perfil_academico] => asdasd
        [estado] => asdass
        [correo] => mailll@gmail.com
        [asistencia] => 1
    )

[1] => Array
    (
        [id_asistente] => 4
        [nombre] => Aasdasdad
        [inst_procedencia] => asdsa
        [perfil_academico] => asdasd
        [estado] => asdasdas
        [correo] => asdasdsa@adasdsa.com
        [asistencia] => 1
    )

[2] => Array
    (
        [id_asistente] => 6
        [nombre] => asdasdas
        [inst_procedencia] => asdasd
        [perfil_academico] => asdasd
        [estado] => asddas
        [correo] => asdasdsa@gmail.com
        [asistencia] => 1
    )
)

这是我尝试下载文件的功能：

function exportToExcel($data, $filename) {
    $spreadsheet = new Spreadsheet();
    $sheet = $spreadsheet->getActiveSheet();
    $sheet->fromArray($data, NULL, 'A1');

    $writer = \PhpOffice\PhpSpreadsheet\IOFactory::createWriter($spreadsheet, 'Xls');
    header('Content-Type: application/vnd.ms-excel');
    header('Content-Disposition: attachment; filename="'.$filename.'.xls"');
    header('Cache-Control: max-age=0');
    $writer->save('php://output');
}

老实说，我不知道这是否与阵列有关，但我想不出其他原因，任何帮助都将不胜感激