利用PHP抓Youtube影片（範例程式）

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<?php
/**
使用前請先下載phpQuery，
否則你需要自己改寫get_meta_data方法的內容
*/
require_once 'libraries/phpQuery.php';  // 請更改為phpQuery的位置

define('lang_ytdl02', '低品質影片', true);
define('lang_ytdl03', '標準品質影片', true);
define('lang_ytdl05', '高畫質影片', true);
define('lang_ytdl06', '超高畫質影片', true);

class ytdl
{
  // 每一個ID代表一種格式，這裡只列基本的部份。其他還有3gp等格式可用......
  private $_format = array(
		'5' =>array('format'=> 'FLV',   'res'=> '240p',  'desc'=> lang_ytdl02),
		'18'=>array('format'=> 'MP4',   'res'=> '360p',  'desc'=> lang_ytdl02),
		'22'=>array('format'=> 'MP4',   'res'=> '720p',  'desc'=> lang_ytdl05),
		'34'=>array('format'=> 'FLV',   'res'=> '360p',  'desc'=> lang_ytdl02),
		'35'=>array('format'=> 'FLV',   'res'=> '480p',  'desc'=> lang_ytdl03),
		'37'=>array('format'=> 'MP4',   'res'=> '1080p', 'desc'=> lang_ytdl06),
		'38'=>array('format'=> 'MP4',   'res'=> '4k',    'desc'=> lang_ytdl06),
		'43'=>array('format'=> 'WebM',  'res'=> '360p',  'desc'=> lang_ytdl02),
		'44'=>array('format'=> 'WebM',  'res'=> '480p',  'desc'=> lang_ytdl03),
		'45'=>array('format'=> 'WebM',  'res'=> '720p',  'desc'=> lang_ytdl05),
		'46'=>array('format'=> 'WebM',  'res'=> '1080p', 'desc'=> lang_ytdl06),
  );
  
  private $_ytid;
  
  /**
  建構子
  string $ytid: Youtube影片ID
  string $memory_limit: 因為抓影片時有可能耗盡記憶體，所以此值可以設大一些。不過256M應該是足夠了......
  */
  public function __construct ($ytid, $memory_limit = '256M') {
    $this->_ytid      = $ytid;
    ini_set('memory_limit', $memory_limit);
    
    if (!class_exists('phpQuery')) {
      throw new Exception('No phpQuery class. Please download it at http://code.googe.com/p/phpQuery');
    }
  }
  
  /**
  取得影片標題與各種解析度的影片位址
  */
  public function get_meta_data () {
    $output           = array('title'=>'', 'videos'=>array());
    
    // 這裡是抓影片播放頁的資料，如果要減少傳輸量的話，可以用http://www.youtube.com/get_video_info?video_id={ytid}，可以少抓很多html廢話，效果也是一樣啦
    $url              = 'http://www.youtube.com/watch?v='.$this->_ytid;
    $ch               = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $content          = curl_exec($ch);
    $info             = curl_getinfo($ch);
    curl_close($ch);
    if ($info['http_code'] > 299 || $info['http_code'] < 200) {
      throw new Exception("Cannot fetch video data");
    }
    
    // 這部份是要抓出影片標題以便掛在影片url用，不過老實說我沒實驗過不加這個會不會怎樣呢？
    $output['title']  = pq('#eow-title', $pq)->attr('title');
    // 接著要來parse影片的位址了
    $pattern          = '#"url_encoded_fmt_stream_map": "([^"]*)"#i';
    preg_match($pattern, $content, $match);
    if (!isset($match[1])) {
      throw new Exception('Cannot parse video information');
    }
    $links            = explode(',', $match[1]);
    foreach ($links as $link) {
      parse_str($link, $d);
      if (!isset($d['url'])) {
        continue;
      }
      $url            = str_replace('\\', '', $d['url']);
      $url            = preg_replace('#(u0026[^&]*)#', '', $url).'&title='.urlencode($output['title']);
      preg_match('#itag\=([0-9]{1,2})#', $url, $tag);
      
      $output['videos'][strval($tag[1])]  = $url;
    }
    
    // 傳回結果
    return $output;
  }
  
  /**
  將影片寫入成為檔案
  string $url: 影片的uri
  string $filename: 要存檔的位址
  */
  public function get_video ($url, $filename) {
    // 先把檔案抓下來
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
    $result = curl_exec($ch);
    $info = curl_getinfo($ch);
    curl_close($ch);
    
    if ($info['http_code'] > 299 || $info['http_code'] < 200) {
      throw new Exception("HTTP Retrieve failed({$info['http_code']})");
    }
    
    // 抓下來以後再寫入
    $fp = fopen($filename, 'w');
    if (!$fp) {
      throw new Exception("File Open Error");
    }
    fwrite($fp, $result);
    fclose($fp);
    return true;
  }
  
}

try {
  $ytid     = "NvB5IhJ-m40";
  $ytdler   = new ytdl($ytid);
  $info     = $ytdler->get_meta_data();
  
  if (!isset($info['videos']['5'])) {
    throw new Exception("Cannot get low resolution video";
  }
  // 抓影片啦
  $filename = $ytid.".mp4";
  $ytdler->get_video($info['videos']['5'], $filename);
} catch (Exception $e) {
  echo 'Error: '.$e->getMessage()."\n";
  die();
}
?>