<?php
require_once 'Youtube.php';
 
$youtube = new Youtube('http://www.youtube.com/watch?v=232AQHdnhTE');
$youtube->setFormat(Youtube::FORMAT_480P);
$info = $youtube->download('./path/the/video/', 'movie_name');

<?php
/**
 * @author Axel ETCHEVERRY
 * @link http://www.axel-etcheverry.com
 * @copyright Copyright (c) 2010, Axel ETCHEVERRY (http://www.axel-etcheverry.com).
 * Displays <a href="http://opensource.org/licenses/gpl-license.php">GNU Public License</a>
 * @license http://opensource.org/licenses/gpl-license.php GNU Public License
 * @version Youtube 1.0
 */
 
/**
 * @see Zend_Json
 */
require_once 'Zend/Json.php';
 
/**
 * @see Zend_Http_Client
 */
require_once 'Zend/Http/Client.php';
 
class Youtube
{
    const FORMAT_360P  = 6;
    const FORMAT_480P  = 18;
    const FORMAT_720P  = 22;
    const FORMAT_1080P = 37;
    /**
     * Youtube id
     *
     * @var string
     * @access protected
     */
    protected $_id;
 
    /**
     * Youtube provider
     * @var string
     * @access protected
     */
    protected $_provider = 'http://www.youtube.com/get_video';
 
    /**
     * Vidéo format
     *
     * @var integer
     * @access protected
     */
    protected $_format;
 
    /**
     * 
     * @param string $url
     */
    public function __construct($url)
    {
        $this->_id = self::getId($url);
    }
 
    /**
     * get yotube id
     *
     * @param string $url
     * @return String
     * @access public
     * @static
     */
    public static function getId($url)
    {
        $url = parse_url($url, PHP_URL_QUERY);
        parse_str($url, $query);
        return $query['v'];
    }
 
    /**
     * set the vidéo format
     *
     * @param integer $format
     * @return Youtube
     * @access public
     */
    public function setFormat($format)
    {
        $this->_format = (int)$format;
        return $this;
    }
 
    /**
     * Download video
     *
     * @param string $path
     * @param string $name
     * @return array
     * @access public
     */
    public function download($path = './', $name = '')
    {
        $content = file_get_contents('http://www.youtube.com/watch?v=' . $this->_id);
 
        preg_match("/'SWF_ARGS': (.*),/", $content, $matches);
        unset($content);
 
        $json = Zend_Json::decode($matches[1]);
        unset($matches);
 
        $client = new Zend_Http_Client();
        $client->setUri($this->_provider . '?video_id=' . $this->_id . '&t=' . urldecode($json['t']) . '&fmt=' . $this->_format);
        unset($json);
 
        $client->setConfig(array(
            'maxredirects' => 0,
            'timeout'      => 30
        ));
 
        $response = $client->request();
 
        unset($client);
 
        $headers = $response->getHeaders();
 
        unset($response);
 
        if(empty($name))
        {
            $name = $this->_id;
        }
 
        $filename = $path . $name . '.mp4';
 
        file_put_contents($filename, file_get_contents($headers['Location']));
 
        unset($headers);
 
        $info = Zend_Json::decode(file_get_contents('http://www.youtube.com/oembed?url=http%3A//www.youtube.com/watch?v%3D' . $this->_id . '&format=json'));
 
        return array(
            'id'     => $this->_id, 
            'format' => $this->_format, 
            'title'  => $info['title'], 
            'file'   => $filename
        );
    }
}