youtube_playlist_to_mp3.php

<?php

// https://github.com/rg3/youtube-dl/

$playlist_id = "PL35E63D54FF7AAFC4";
//$playlist_id = "PL91D82848DC945315";
$max_results = 10;
$start_index = 1;

do {
	$url = sprintf(
		"https://gdata.youtube.com/feeds/api/playlists/%s?v=2&alt=json&max-results=%d&start-index=%d",
		$playlist_id,
		(int)$max_results,
		(int)$start_index
	);
	$json = json_decode(file_get_contents($url), true);

	foreach ($json["feed"]["entry"] as $entry) {
		$cmd = sprintf(
			'/home/salvarez/opt/youtube-dl -o "%%(title)s.%%(ext)s" %s --restrict-filenames -v --newline --buffer-size=10240 --extract-audio --audio-format=mp3 --add-metadata --audio-quality=0',
			escapeshellarg($entry["media\$group"]["media\$player"]["url"])
		);
		passthru($cmd);
	}

	$start_index += $max_results;

} while ($start_index <= $json["feed"]["openSearch\$totalResults"]["\$t"]);