PHPExcel を使用して Excel ファイルを処理するにはどうすればよいですか?

require_once 'PHPExcel/Classes/PHPExcel.php';

$excel = new PHPExcel();

$excel->setActiveSheetIndex(0);

$excel->getActiveSheet()->setCellValue('A1', '姓名')
                        ->setCellValue('B1', '年龄')
                        ->setCellValue('C1', '邮箱');

$excel->getActiveSheet()->setCellValue('A2', '张三')
                        ->setCellValue('B2', 20)
                        ->setCellValue('C2', 'zhangsan@example.com');

$excel->getActiveSheet()->setCellValue('A3', '李四')
                        ->setCellValue('B3', 25)
                        ->setCellValue('C3', 'lisi@example.com');

$excel->getActiveSheet()->setCellValue('A4', '王五')
                        ->setCellValue('B4', 30)
                        ->setCellValue('C4', 'wangwu@example.com');

header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="example.xls"');
header('Cache-Control: max-age=0');

$writer = PHPExcel_IOFactory::createWriter($excel, 'Excel5');
$writer->save('php://output');

$objReader = PHPExcel_IOFactory::createReader('Excel5');

$objReader->setReadDataOnly(true);

$objPHPExcel = $objReader->load("example.xls");

$worksheet = $objPHPExcel->getActiveSheet();

foreach ($worksheet->getRowIterator() as $row) {
    $cellIterator = $row->getCellIterator();
    $cellIterator->setIterateOnlyExistingCells(false);

    $columns = [];

    foreach ($cellIterator as $cell) {
        $columns[] = $cell->getValue();
    }

    if (count($columns) > 0) {
        echo implode('|', $columns) . "
";
    }
}

$pdo = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');

$sql = "SELECT name, age, email FROM users";

$stmt = $pdo->query($sql);

$excel = new PHPExcel();

$excel->setActiveSheetIndex(0);

$excel->getActiveSheet()->setCellValue('A1', '姓名')
                        ->setCellValue('B1', '年龄')
                        ->setCellValue('C1', '邮箱');

$i = 2;

while ($row = $stmt->fetch()) {
    $excel->getActiveSheet()->setCellValue('A' . $i, $row['name'])
                            ->setCellValue('B' . $i, $row['age'])
                            ->setCellValue('C' . $i, $row['email']);
    $i++;
}

header('Content-Type: application/vnd.ms-excel');
header('Content-Disposition: attachment;filename="users.xls"');
header('Cache-Control: max-age=0');

$writer = PHPExcel_IOFactory::createWriter($excel, 'Excel5');
$writer->save('php://output');