// https://stackoverflow.com/questions/157318/resumable-downloads-when-using-php-to-send-the-file
if (!class_exists('UpdraftPlus_NonExistentFileException')):
class UpdraftPlus_NonExistentFileException extends RuntimeException {}
if (!class_exists('UpdraftPlus_UnreadableFileException')):
class UpdraftPlus_UnreadableFileException extends RuntimeException {}
if (!class_exists('UpdraftPlus_UnsatisfiableRangeException')):
class UpdraftPlus_UnsatisfiableRangeException extends RuntimeException {}
if (!class_exists('UpdraftPlus_InvalidRangeHeaderException')):
class UpdraftPlus_InvalidRangeHeaderException extends RuntimeException {}
class UpdraftPlus_RangeHeader
* The first byte in the file to send (0-indexed), a null value indicates the last
* The last byte in the file to send (0-indexed), a null value indicates $start to
* Create a new instance from a Range header string
* @return UpdraftPlus_RangeHeader
public static function createFromHeaderString($header)
if (!preg_match('/^\s*([A-Za-z]+)\s*=\s*(\d*)\s*-\s*(\d*)\s*(?:,|$)/', $header, $info)) {
throw new UpdraftPlus_InvalidRangeHeaderException('Invalid header format');
} else if (strtolower($info[1]) !== 'bytes') {
throw new UpdraftPlus_InvalidRangeHeaderException('Unknown range unit: ' . $info[1]);
$info[2] === '' ? null : $info[2],
$info[3] === '' ? null : $info[3]
* @param int|null $firstByte
* @param int|null $lastByte
* @throws UpdraftPlus_InvalidRangeHeaderException
public function __construct($firstByte, $lastByte)
$this->firstByte = $firstByte === null ? $firstByte : (int)$firstByte;
$this->lastByte = $lastByte === null ? $lastByte : (int)$lastByte;
if ($this->firstByte === null && $this->lastByte === null) {
throw new UpdraftPlus_InvalidRangeHeaderException(
'Both start and end position specifiers empty'
} else if ($this->firstByte < 0 || $this->lastByte < 0) {
throw new UpdraftPlus_InvalidRangeHeaderException(
'Position specifiers cannot be negative'
} else if ($this->lastByte !== null && $this->lastByte < $this->firstByte) {
throw new UpdraftPlus_InvalidRangeHeaderException(
'Last byte cannot be less than first byte'
* Get the start position when this range is applied to a file of the specified size
* @throws UpdraftPlus_UnsatisfiableRangeException
public function getStartPosition($fileSize)
if ($this->firstByte === null) {
return ($size - 1) - $this->lastByte;
if ($size <= $this->firstByte) {
throw new UpdraftPlus_UnsatisfiableRangeException(
'Start position is after the end of the file'
* Get the end position when this range is applied to a file of the specified size
* @throws UpdraftPlus_UnsatisfiableRangeException
public function getEndPosition($fileSize)
if ($this->lastByte === null) {
if ($size <= $this->lastByte) {
throw new UpdraftPlus_UnsatisfiableRangeException(
'End position is after the end of the file'
* Get the length when this range is applied to a file of the specified size
* @throws UpdraftPlus_UnsatisfiableRangeException
public function getLength($fileSize)
return $this->getEndPosition($size) - $this->getStartPosition($size) + 1;
* Get a Content-Range header corresponding to this Range and the specified file
public function getContentRangeHeader($fileSize)
return 'bytes ' . $this->getStartPosition($fileSize) . '-'
. $this->getEndPosition($fileSize) . '/' . $fileSize;
class UpdraftPlus_PartialFileServlet
* The range header on which the data transmission will be based
* @var UpdraftPlus_RangeHeader|null
* @param UpdraftPlus_RangeHeader $range Range header on which the transmission will be based
public function __construct($range = null)
* Send part of the data in a seekable stream resource to the output buffer
* @param resource $fp Stream resource to read data from
* @param int $start Position in the stream to start reading
* @param int $length Number of bytes to read
* @param int $chunkSize Maximum bytes to read from the file in a single operation
private function sendDataRange($fp, $start, $length, $chunkSize = 2097152)
fseek($fp, $start, SEEK_SET);
$read = ($length > $chunkSize) ? $chunkSize : $length;
* Send the headers that are included regardless of whether a range was requested
* @param string $fileName
* @param int $contentLength
* @param string $contentType
private function sendDownloadHeaders($fileName, $contentLength, $contentType)
header('Content-Type: ' . $contentType);
header('Content-Length: ' . $contentLength);
header('Content-Disposition: attachment; filename="' . $fileName . '"');
header('Accept-Ranges: bytes');
* Send data from a file based on the current Range header
* @param string $path Local file system path to serve
* @param string $contentType MIME type of the data stream
public function sendFile($path, $contentType = 'application/octet-stream')
// Make sure the file exists and is a file, otherwise we are wasting our time
$localPath = realpath($path);
if ($localPath === false || !is_file($localPath)) {
throw new UpdraftPlus_NonExistentFileException(
$path . ' does not exist or is not a file'
// Make sure we can open the file for reading
if (!$fp = fopen($localPath, 'r')) {
throw new UpdraftPlus_UnreadableFileException(
'Failed to open ' . $localPath . ' for reading'
$fileSize = filesize($localPath);
if ($this->range == null) {
// No range requested, just send the whole file
header('HTTP/1.1 200 OK');
$this->sendDownloadHeaders(basename($localPath), $fileSize, $contentType);
// Send the request range
header('HTTP/1.1 206 Partial Content');
header('Content-Range: ' . $this->range->getContentRangeHeader($fileSize));
$this->sendDownloadHeaders(
$this->range->getLength($fileSize),
$this->range->getStartPosition($fileSize),
$this->range->getLength($fileSize)
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
