php 实现文件下载，兼容IE、Firefox、Chrome等浏览器

一、下载任意文件：

Header ( "Content-type: application/octet-stream" );
$ua = $_SERVER ["HTTP_USER_AGENT"];
$file = '/var/www/tmp.txt';
$filename = basename ( $file );
$encoded_filename = rawurlencode ( $filename );
if (preg_match ( "/MSIE/", $ua )) {
    header ( 'Content-Disposition: attachment; filename="' . $encoded_filename . '"' );
} else if (preg_match ( "/Firefox/", $ua )) {
    header ( "Content-Disposition: attachment; filename*=\"utf8''" . $filename . '"' );
} else {
    header ( 'Content-Disposition: attachment; filename="' . $filename . '"' );
}
header ( "Content-Length: " . filesize ( $file ) );
readfile ( $file );

二、PHPExcel导出excel文件下载：

　　　　 ...
        $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
        header('Content-Type: application/vnd.ms-excel');
        $ua = $_SERVER["HTTP_USER_AGENT"];
        $encoded_filename = rawurlencode($filename);
        if (preg_match("/MSIE/", $ua)) {
            header('Content-Disposition: attachment; filename="' . $encoded_filename . '"');
        } else if (preg_match("/Firefox/", $ua)) {
            header("Content-Disposition: attachment; filename*=\"utf8''" . $filename . '"');
        } else {
            header('Content-Disposition: attachment; filename="' . $filename . '"');
        }
        header('Cache-Control: max-age=0');
        $objWriter->save('php://output');