Eventualmente tropecé con esta publicación: http://w-shadow.com/blog/2007/08/12/how-to-force-file-download-with-php/.
function output_file($file, $name, $mime_type='')
{
/*
This function takes a path to a file to output ($file),
the filename that the browser will see ($name) and
the MIME type of the file ($mime_type, optional).
If you want to do something on download abort/finish,
register_shutdown_function('function_name');
*/
if(!is_readable($file)) die('File not found or inaccessible!');
$size = filesize($file);
$name = rawurldecode($name);
/* Figure out the MIME type (if not specified) */
$known_mime_types=array(
"pdf" => "application/pdf",
"txt" => "text/plain",
"html" => "text/html",
"htm" => "text/html",
"exe" => "application/octet-stream",
"zip" => "application/zip",
"doc" => "application/msword",
"xls" => "application/vnd.ms-excel",
"ppt" => "application/vnd.ms-powerpoint",
"gif" => "image/gif",
"png" => "image/png",
"jpeg"=> "image/jpg",
"jpg" => "image/jpg",
"php" => "text/plain"
);
if($mime_type==''){
$file_extension = strtolower(substr(strrchr($file,"."),1));
if(array_key_exists($file_extension, $known_mime_types)){
$mime_type=$known_mime_types[$file_extension];
} else {
$mime_type="application/force-download";
};
};
ob_end_clean(); //turn off output buffering to decrease cpu usage
// required for IE, otherwise Content-Disposition may be ignored
if(ini_get('zlib.output_compression'))
ini_set('zlib.output_compression', 'Off');
header('Content-Type: ' . $mime_type);
header('Content-Disposition: attachment; filename="'.$name.'"');
header("Content-Transfer-Encoding: binary");
header('Accept-Ranges: bytes');
/* The three lines below basically make the
download non-cacheable */
header("Cache-control: private");
header('Pragma: private');
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
// multipart-download and download resuming support
if(isset($_SERVER['HTTP_RANGE']))
{
list($a, $range) = explode("=",$_SERVER['HTTP_RANGE'],2);
list($range) = explode(",",$range,2);
list($range, $range_end) = explode("-", $range);
$range=intval($range);
if(!$range_end) {
$range_end=$size-1;
} else {
$range_end=intval($range_end);
}
$new_length = $range_end-$range+1;
header("HTTP/1.1 206 Partial Content");
header("Content-Length: $new_length");
header("Content-Range: bytes $range-$range_end/$size");
} else {
$new_length=$size;
header("Content-Length: ".$size);
}
/* output the file itself */
$chunksize = 1*(1024*1024); //you may want to change this
$bytes_send = 0;
if ($file = fopen($file, 'r'))
{
if(isset($_SERVER['HTTP_RANGE']))
fseek($file, $range);
while(!feof($file) &&
(!connection_aborted()) &&
($bytes_send<$new_length)
)
{
$buffer = fread($file, $chunksize);
print($buffer); //echo($buffer); // is also possible
flush();
$bytes_send += strlen($buffer);
}
fclose($file);
} else die('Error - can not open file.');
die();
}
/*********************************************
Example of use
**********************************************/
/*
Make sure script execution doesn't time out.
Set maximum execution time in seconds (0 means no limit).
*/
set_time_limit(0);
$file_path='that_one_file.txt';
output_file($file_path, 'some file.txt', 'text/plain');
Sumando todas las cabeceras recomendados allí y también usando:
ob_end_clean(); //turn off output buffering to decrease cpu usage
antes de cualquier salida - ha ayudado. No más limitaciones observables. Los archivos se descargan completamente, incluso los más grandes.
PHP no tiene tal límite. Esto debe hacerse en serverfault ya que está relacionado con su configuración de Apache. – hobodave