I am working on a video site that has different movies and videos which users can stream and download. Now I am being asked to implement a download restriction in such a way that only 1 video can be downloaded at a time. There are two servers: my files and database are on one server and the videos are on the other.
What I am doing for downloading is to send a request from the first server for a file on the other server. If the requested video exists, it is downloaded.
Now I want to restrict the users so that if they are already downloading a video, they cannot download another until the current download completes. Once the current download has completed, the user can download the next video. I have not seen any function that enables a developer to know when the download has completed.
I have a few things in my mind about storing the information of the download time in the database. But storing the time of download is not my requirement.
What is the best way to implement this? Is there an event from which we can detect the download end time? Is there any solution to this? I am using PHP and here is the code that I have used for downloading the file from the second (videos) server. This file sends a request with a file name and full path. The $real_file variable contains the file name along with full path on the second server.
if(file_exists($real_file))
{
header("Pragma: public");
header("Cache-Control: private");
header("Expires: 0");
header('Cache-Control: no-store, no-cache, must-revalidate');
header('Cache-Control: pre-check=0, post-check=0, max-age=0');
header('Content-Transfer-Encoding: binary');
header('Content-Encoding: none');
header("Content-Disposition: attachment; filename=".urlencode(basename($real_file)));
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
header("Content-Description: File Transfer");
header("Content-Length: " . filesize($real_file));
header("Accept-Length: ".filesize($real_file));
$fp = #fopen($real_file, "rb");
while(!feof($fp))
{
$buffer= fread($fp, 8192);
echo $buffer;
}
#flush();
#ob_flush();
die();
}
If you stream the file through a php-script, it would maybe be able to obtain a lock for a specific user (logged in of course) before you start to read the file and outputting to the stream:
(pseudocode)
obtain_lock_somehow();
readfile('yourvideofile.mpg');
release_lock();
I don't know how the script would respond to a closed connection, and it might force the script to end prematurely.
Another option would be to read the file and pass on to the stream in "chunks", and in between every chunk you update the status of the visitors "lock", so that you can identify at which last timestamp the visitor actually downloaded something.
(pseudocode)
while(file_is_not_finished) {
update_lock_status();
pass_thru_buffer();
}
But do note that streaming huge amount of data in a php-script like this is probably not the best way to go, and you might be better off with a native server module for it.
Related
I wrote a download script in PHP as specified below, my script is downloading the files correctly, but I am feeling that the browser(chrome) progress bar is not getting updated properly in regular intervals.
My file is of size 320MB, while downloading that file the progress is getting updated randomly as "11MB, 76MB, 200Mb & 320MB" or "70MB & 320MB" etc.
In most of the sites download progress update is happening in constant chunks like after every MB, so I want to know how we can control the progress update intervals, may be by sending some extra headers or something else.
I want to improve the user experience by updating the progress in constant intervals, so anybody please help me to handle this situation in a proper way.
// HTTP Headers for ZIP File Downloads
// http://perishablepress.com/press/2010/11/17/http-headers-file-downloads/
// file variables
$filename = "Movie Tunes.zip";
$filepath = "files/";
// http headers for zip downloads
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: public,must-revalidate, post-check=0, pre-check=0");
header("Content-Description: File Transfer"); // MIME
header("Content-type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"".$filename."\"");
header("Content-Transfer-Encoding: binary"); // MIME
header("Content-Length: ".filesize($filepath.$filename));
ob_end_flush();
#readfile($filepath.$filename);
Thanks,
Siva
No, you cannot influence when/how the browser updates its download progress bar.
I am creating a PDF file from raw binary data and it's working perfectly but because of the headers that I define in my PHP file it prompts the user either to "save" the file or "open with". Is there any way that I can save the file on local server somewhere here http://localhost/pdf?
Below are the headers I have defined in my page
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Type: application/pdf");
header("Content-Disposition: attachment; filename=$filename");
header("Content-Transfer-Encoding: binary");
If you would like to save the file on the server rather than have the visitor download it, you won't need the headers. Headers are for telling the client what you are sending them, which is in this case nothing (although you are likely displaying a page linking to you newly created PDF or something).
So, instead just use a function such as file_put_contents to store the file locally, eventually letting your web server handle file transfer and HTTP headers.
// Let's say you have a function `generate_pdf()` which creates the PDF,
// and a variable $pdf_data where the file contents are stored upon creation
$pdf_data = generate_pdf();
// And a path where the file will be created
$path = '/path/to/your/www/root/public_html/newly_created_file.pdf';
// Then just save it like this
file_put_contents( $path, $pdf_data );
// Proceed in whatever way suitable, giving the user feedback if needed
// Eg. providing a download link to http://localhost/newly_created_file.pdf
You can use output control functions. Place ob_start() at beginning of your script. At the end use ob_get_contents() and save the content to a local file.
After that you can use ob_end_clean() or ob_end_flush() depending on whether you want to output PDF to browser as well, or you would redirect user to some other page. If you use ob_end_flush() make sure you set the headers before flushing the data.
I need to know if a user selected download then clicked the cancel button, which is not the same as readfile having an error. I have inspected the count returned by the readfile function, but it shows the bytes in the file even if the user canceled the download from the Save As dialog.
The reason this is needed is because my site has a one-time download, where a member gives permission for another use to download their file one time, then the permission goes away. But if a member clicks the download button then decides not to download it right then, I dont' want my database to get updated to show they got the file.
This deals with intellectual property protection since the files are the property of the member who uploaded them, and I need to keep an audit trail of exactly what other members downloaded the file in case they start floating around the internet. But if the readfile function always reflects the filesize (meaning those bytes were transferred in some way), I have no way to know if the file was actually downloaded.
I have seen a number of posts about this subject, but no real solutions to what has to be a frequent need - did they download it or not? Just knowing that they clicked the download button doesn't really say whether they decided to go through with it since the Save As dialog box allows someone to cancel the actual completion of the download.
For completeness, here is my download code up until the readfile function:
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header("Content-Disposition: attachment; filename=$download_name");
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . filesize("sub/$doc_file"));
ob_clean();
flush();
$wasdownloaded = readfile("sub/$doc_file");
I fear the correct answer is "Impossible" - let me explain: You might be able to correctly figure out, when the file has crossed the wire, but you can't figure out reliably, whether the client threw it away or not.
Example (chronological sequence):
A user on MSIE clicks download and is presented with the "Save where" Dialog.
While this dialog is open, the download is started in the background.
The user navigates around in the dialog or simply does nothing (phone rang, he talks)
The background download is finished, your script sees the download as complete
The user clicks on "cancel"
MSIE deletes the tempfile, the download is never stored in a user-accessible form
Result:
The user sees the file as "not downloaded" - and he is correct
Your app sees the file as "correctly downloaded" - and it is correct
You would first need ignore_user_abort().
This would allow your script to continue on after the user has hit cancel, or escape.
You would then have to print out the file and continuously check with connection_aborted().
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header("Content-Disposition: attachment; filename=$download_name");
header('Content-Transfer-Encoding: binary');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Pragma: public');
header('Content-Length: ' . filesize("sub/$doc_file"));
ob_clean();
flush();
$fp=fopen("sub/$doc_file","rb");
while(!feof($fp))
{
print(fread($fp,1024*8));
flush();
ob_flush();
if( connection_aborted() )
{
//do code for handling aborts
}
}
Use this comment on php.net : http://www.php.net/manual/en/function.fread.php#72716
On fclose you would be able to determine if file has been downloaded successful, because your are checking if user aborted connection with connection_status()
I am coding a file sharing application for my office. One strange problem I am going through is the Illustrator files being opened in PDF when you hit the download button.
This problem is triggered because the mime type of illustrator files is application/pdf. So the browser when it reads the file, triggers Acrobat to open the file. Is there any way I could instruct the browser to open the file in Illustrator?
Or is there any way to modify the mime type after uploading the file? The backend code is PHP.
Thank you for any help.
One way to do this is to force the browser to display the "download file"-dialog. So the user can decide what to do with the file.
This can be done via PHP-Headers. (http://www.php.net/manual/en/function.header.php#83384)
There is also an example on how to this (Post 83384):
<?php
// downloading a file
$filename = $_GET['path'];
// fix for IE catching or PHP bug issue
header("Pragma: public");
header("Expires: 0"); // set expiration time
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
// browser must download file from server instead of cache
// force download dialog
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");
// use the Content-Disposition header to supply a recommended filename and
// force the browser to display the save dialog.
header("Content-Disposition: attachment; filename=".basename($filename).";");
/*
The Content-transfer-encoding header should be binary, since the file will be read
directly from the disk and the raw bytes passed to the downloading computer.
The Content-length header is useful to set for downloads. The browser will be able to
show a progress meter as a file downloads. The content-lenght can be determines by
filesize function returns the size of a file.
*/
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".filesize($filename));
#readfile($filename);
exit(0);
?>
When using this example please consider that using
$filename = $_GET['path'];
is a big security problem. You should work with something like ID's instead or validate the input.
For example:
if($_GET['file'] == 1) {
$filename = foobar.pdf;
} elseif($_GET['file'] == 2) {
$filename = foo.pdf;
} else {
die();
}
Normally, when I want to allow a user to download a file without revealing the exact location, I just use something like this to let them download the file:
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment; filename=\"" . $filename) . "\";");
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . filesize($filename));
readfile("$filename");
But if they are using a modern browser or other download client, and they pause the download and try to resume it, the script (assuming they are still authenticated or whatever) will resend the headers and the file contents from the beginning, thus breaking the download, and basically requiring the file to be redownloaded from the beginning.
How can I enable my script to compensate for paused (and consequentially, resumed) downloads?
Use php's built-in fopen to open the file and then fseek to the right place (based on the range in the request header) and then return the partial file using fpassthru instead of using readfile.
You can find some example code in php under the comments for fread
You need to read the request headers like Range, If-Range, etc then seek to the correct location in the file. Normally a web-server would do this for you on an ordinary file. It's a bit complex but here's something that might get you started:
http://forums.asp.net/t/1218116.aspx
http://www.notes411.com/dominosource/tips.nsf/0/480C4E3BE825F69D802571BC007D5AC9!opendocument
For the second link the code is in part 12