<?php

	$id = 'yTDL5XZTLrU';
	$url = 'https://www.youtube.com/watch?v=yTDL5XZTLrU';

	// youtube-dl https://www.youtube.com/watch?v=yTDL5XZTLrU -x -k --audio-quality 0 --prefer-ffmpeg -o "%(id)s.%(ext)s"
	system('youtube-dl ' . $url . ' -x -k --audio-quality 0 --prefer-ffmpeg -o "%(id)s.%(ext)s"');