php文件下载

public function down()
{
$lang = strtolower(cookie('think_language'));

if ($lang == 'en-us') {
$filename = '1.pdf';
} elseif ($lang == 'es-us') {

//....
$filename = '2.pdf';
} else {
$filename = '3.pdf';
}

if (false === is_file($filename)) {
exit('file does not exist');
}

// http headers

//Some browsers have troubles with force-download. use 'Content-Type: application/octet-stream'

header('Content-Type: application-x/force-download');
header('Content-Disposition: attachment; filename="' . basename($filename) . '"');
header('Content-length: ' . filesize($filename));

// for IE6
if (false === strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE 6')) {
header('Cache-Control: no-cache, must-revalidate');
}
header('Pragma: no-cache');

// read file content and output
return readfile($filename);
}