Is there a good implementation of partial file downloading in PHP?
Seems that I found what I needed myself. So that other may benefit from this, here is the link: http://www.coneural.org/florian/papers/04_byteserving.php
And just in case the original page stops to work (the script is pretty old already), here is a copy of it:
<?php /*The following byte serving code is (C) 2004 Razvan Florian. You may find the latest version at http://www.coneural.org/florian/papers/04_byteserving.php*/function set_range($range, $filesize, &$first, &$last){ /* Sets the first and last bytes of a range, given a range expressed as a string and the size of the file. If the end of the range is not specified, or the end of the range is greater than the length of the file, $last is set as the end of the file. If the begining of the range is not specified, the meaning of the value after the dash is "get the last n bytes of the file". If $first is greater than $last, the range is not satisfiable, and we should return a response with a status of 416 (Requested range not satisfiable). Examples: $range='0-499', $filesize=1000 => $first=0, $last=499 . $range='500-', $filesize=1000 => $first=500, $last=999 . $range='500-1200', $filesize=1000 => $first=500, $last=999 . $range='-200', $filesize=1000 => $first=800, $last=999 . */ $dash=strpos($range,'-'); $first=trim(substr($range,0,$dash)); $last=trim(substr($range,$dash+1)); if ($first=='') { //suffix byte range: gets last n bytes $suffix=$last; $last=$filesize-1; $first=$filesize-$suffix; if($first<0) $first=0; } else { if ($last=='' || $last>$filesize-1) $last=$filesize-1; } if($first>$last){ //unsatisfiable range header("Status: 416 Requested range not satisfiable"); header("Content-Range: */$filesize"); exit; }}function buffered_read($file, $bytes, $buffer_size=1024){ /* Outputs up to $bytes from the file $file to standard output, $buffer_size bytes at a time. */ $bytes_left=$bytes; while($bytes_left>0 && !feof($file)){ if($bytes_left>$buffer_size) $bytes_to_read=$buffer_size; else $bytes_to_read=$bytes_left; $bytes_left-=$bytes_to_read; $contents=fread($file, $bytes_to_read); echo $contents; flush(); }}function byteserve($filename){ /* Byteserves the file $filename. When there is a request for a single range, the content is transmitted with a Content-Range header, and a Content-Length header showing the number of bytes actually transferred. When there is a request for multiple ranges, these are transmitted as a multipart message. The multipart media type used for this purpose is "multipart/byteranges". */ $filesize=filesize($filename); $file=fopen($filename,"rb"); $ranges=NULL; if ($_SERVER['REQUEST_METHOD']=='GET' && isset($_SERVER['HTTP_RANGE']) && $range=stristr(trim($_SERVER['HTTP_RANGE']),'bytes=')){ $range=substr($range,6); $boundary='g45d64df96bmdf4sdgh45hf5';//set a random boundary $ranges=explode(',',$range); } if($ranges && count($ranges)){ header("HTTP/1.1 206 Partial content"); header("Accept-Ranges: bytes"); if(count($ranges)>1){ /* More than one range is requested. */ //compute content length $content_length=0; foreach ($ranges as $range){ set_range($range, $filesize, $first, $last); $content_length+=strlen("\r\n--$boundary\r\n"); $content_length+=strlen("Content-type: application/pdf\r\n"); $content_length+=strlen("Content-range: bytes $first-$last/$filesize\r\n\r\n"); $content_length+=$last-$first+1; } $content_length+=strlen("\r\n--$boundary--\r\n"); //output headers header("Content-Length: $content_length"); //see http://httpd.apache.org/docs/misc/known_client_problems.html for an discussion of x-byteranges vs. byteranges header("Content-Type: multipart/x-byteranges; boundary=$boundary"); //output the content foreach ($ranges as $range){ set_range($range, $filesize, $first, $last); echo "\r\n--$boundary\r\n"; echo "Content-type: application/pdf\r\n"; echo "Content-range: bytes $first-$last/$filesize\r\n\r\n"; fseek($file,$first); buffered_read ($file, $last-$first+1); } echo "\r\n--$boundary--\r\n"; } else { /* A single range is requested. */ $range=$ranges[0]; set_range($range, $filesize, $first, $last); header("Content-Length: ".($last-$first+1) ); header("Content-Range: bytes $first-$last/$filesize"); header("Content-Type: application/pdf"); fseek($file,$first); buffered_read($file, $last-$first+1); } } else{ //no byteserving header("Accept-Ranges: bytes"); header("Content-Length: $filesize"); header("Content-Type: application/pdf"); readfile($filename); } fclose($file);}function serve($filename, $download=0){ //Just serves the file without byteserving //if $download=true, then the save file dialog appears $filesize=filesize($filename); header("Content-Length: $filesize"); header("Content-Type: application/pdf"); $filename_parts=pathinfo($filename); if($download) header('Content-disposition: attachment; filename='.$filename_parts['basename']); readfile($filename);}//unset magic quotes; otherwise, file contents will be modifiedset_magic_quotes_runtime(0);//do not send cache limiter headerini_set('session.cache_limiter','none');$filename='myfile.pdf'; //this is the PDF file that will be byteservedbyteserve($filename); //byteserve it!?>
You should be using PEAR HTTP_Download. It is pretty easy to use and it allows download resuming just file:
http://pear.php.net/manual/en/package.http.http-download.intro.php
Based on this:
http://w-shadow.com/blog/2007/08/12/how-to-force-file-download-with-php/
(which you also could use)
I've made a small lib that does what PECL http_send_file extension does:
http://php.net/manual/en/function.http-send-file.php
(which you also could use)
The lib resembles the http_send_file, but if you don't have the option of installing the PECL lib, you could use the http-send-file lib: