Pony.fm/app/models/PlaylistDownloader.php

<?php

	class PlaylistDownloader {
		private $_playlist;
		private $_format;

		function __construct($playlist, $format) {
			$this->_playlist = $playlist;
			$this->_format = $format;
		}

		function download() {
			$zip = new ZipStream($this->_playlist->user->display_name . ' - ' . $this->_playlist->title . '.zip');
			$zip->setComment(
				'Playlist: '. $this->_playlist->title ."\r\n".
				'Curator: '	. $this->_playlist->user->display_name ."\r\n".
				'URL: '		. $this->_playlist->url ."\r\n"."\r\n".
				'Downloaded on '. date('l, F jS, Y, \a\t h:i:s A') . '.'
			);

			$notes =
				'Playlist: '. $this->_playlist->title ."\r\n".
				'Curator: '	. $this->_playlist->user->display_name ."\r\n".
				'URL: '		. $this->_playlist->url ."\r\n".
				"\r\n".
				$this->_playlist->description ."\r\n".
				"\r\n".
				"\r\n".
				'Tracks' ."\r\n".
				"\r\n";

			$m3u = '';
			$index = 1;
			foreach ($this->_playlist->tracks as $track) {
				if (!$track->is_downloadable)
					continue;

				$trackTarget = $track->downloadDirectory . '/' . $track->getDownloadFilenameFor($this->_format);
				$zip->addLargeFile($track->getFileFor($this->_format), $trackTarget);
				$notes .=
					$index . '. ' . $track->title ."\r\n".
					$track->description ."\r\n".
					"\r\n";

				$m3u .= '#EXTINF:' . $track->duration . ',' . $track->title . "\r\n";
				$m3u .= '../' . $trackTarget . "\r\n";

				$index++;
			}

			$playlistDir = 'Pony.fm Playlists/';
			$zip->addFile($notes, $playlistDir . $this->_playlist->title . '.txt');
			$zip->addFile($m3u, $playlistDir . $this->_playlist->title . '.m3u');
			$zip->finalize();
		}
	}