FileServe.class.php

<?php
/**
 * FileServe
 *
 * Class that serves a file from disk to a client.
 *
 * @package		FileServe
 * @author		Kenny <[email protected]>
 * @license		The Unlicense (http://unlicense.org)
*/
class FileServe {
	private $stream;
	private $filename;
	
	const FILE_BUFFER = 8192; //buffer 8192 KByte of the file on every read. You might want to play with this value.
	const CONTENT_TYPE = "application/octet-stream";
	
	/**
	 ** Constructor
	 *
	 * Called when instantiating the class.
	 *
	 * @param str $filename Filename of the file to be read.
	 * @throws Exception if input file doesn't exist or cannot be read
	 */
	public function __construct($filename) {
		if(!file_exists($filename)) throw new Exception("The given input file does not exist.");
		$this->stream = fopen($filename, 'r');
		$this->filename = basename($filename);
		
		if($this->stream === false) throw new Exception("Could not read file. Please check permissions.");
		else return true;
	}
	
	/**
	 * Serve file
	 *
	 * Starts serving the file to the client.
	 *
	 * @throws Exception if stream dead or file empty
	 * @param $throttle (optional) Defines amount of throttle in the transmission in nanoseconds. Defaults to no throttle.
	 * @return true after transmission completed
	 */
	public function serve($throttle = 0) {
		if(!is_resource($this->stream)) throw new Exception("The stream has gone away. This should not occur.");
		if(feof($this->stream)) throw new Exception("The file is empty.");
		
		header('Content-Type: ' . self::CONTENT_TYPE);
		header('Content-Transfer-Encoding: Binary');
		header('Content-disposition: attachment: filename="' . $this->filename . '"');
		
		do {
			echo $fileChunk;
			if($throttle > 0) usleep($throttle);
		} while (false !== ($fileChunk = $this->readChunk()));
		
		return true;
	}
	
	/**
	 * Get next chunk
	 *
	 * Gets a chunk from the file and returns it.
	 *
	 * @return str chunk if chunk read correctly, false if file pointer is EOF
	 */
	 private function readChunk() {
	 	if(feof($this->stream)) return false;
	 	$chunk = fread($this->stream, self::FILE_BUFFER);
	 	return $chunk;
	 }
}

/* Example usage */
$fSrv = new FileServe("debian-8.4.0-amd64-netinst.iso");
$fSrv->serve();