// 利用nginx直接下载文件，提高效率
public function download_apk_efficient($internal_file_path,$file_name){
// And redirect user to internal location
header("Content-Type: application/vnd.android.package-archive");
header("Content-Disposition: attachment; filename=".$file_name);
header("X-Accel-Redirect: " . $internal_file_path);
}
调用的：
Module::factory("Download")->download_apk_efficient("/promoter_files/". $relative_file_path, $out_name); //promoter_files是在nginx的innernal中配置的路径，例如我下载/server/hosting/mobilechannel/promoter_download2/12/1.file，这里实际调用的是download_apk_efficient("/promoter_files/12/1.file" ,$out_name)
在nginx里配置：
location /promoter_files/ { #/promoter_files/是我取的名字，表示alias字段代表的路径
internal;
alias /server/hosting/mobilechannel/promoter_download2/; #这里是文件的实际路径
}