Recently, while making some additions to the Music Page, I came across the need to get the location of a YouTube FLV. Unfortunately, most of my googling turned up outdated results that no longer work. Fortunately, unlike a certain other site, it's not impossible. Below is a quick explanation of what I got to work. I'll be assuming that you know how to get your hands on the video ID (the "v" parameter in the query string).

There really is only one thing that's needed by YouTube to get the video file, and that's the video token. As far as I can tell, this is a time sensitive key that is generated for the user to prevent abuse on the YouTube servers. Luckily, this is pretty easy to obtain. The get_video_info page returns not only the token, but all sorts of other valuable information about the video, such as author, date uploaded, length in seconds, etc. Here's a small function that retrieves this information and returns it as an object:

function ytGetInfo ($id)
{
    $file = file_get_contents ("http://www.youtube.com/get_video_info?&video_id=$id");
    $a = explode ("&", urldecode ($file));
    foreach ($a as $i) {
        $e = explode ("=", $i, 2);
        $ret->$e[0] = $e[1];
    }
    return $ret;
}

Simple stuff, really. The contents of get_video_info are retrieved and stored in $file. This information comes URL encoded, so we first need to decode that. As with any URL string, each variable is separated by an ampersand (&), so when calling explode. That returns the variable/value pairs in an array ([0]=>"author=dxprog", [1]=>"token=asi940tnas", ...). Iterating through each of those, we then explode the var/value pairs and add them to our outgoing object. Now we have the token (amongst other info), so next will be retrieving the video file itself.

YouTube uses get_video to return where the actual video is stored. Now, I don't know all the nuances of this method, but as of this writing, it returns a 303 See other HTTP response code with the location header pointing to the actual, real address of the video file. We'll functionize that:

function ytGetVideoPath ($id)
{
    $info = ytGetInfo ($id);
    $token = $info->token;
    $headers = get_headers ("http://www.youtube.com/get_video?video_id=$id&t=$token&fmt=18");
    foreach ($headers as $item) {
        if (strpos ($item, "Location: ") !== false) {
            return str_replace ("Location: ", "", $item);
        }
    }
    return false;
}

First thing this function does is grab the video information so that we can get the token. We then retrieve the headers of the video providing the video ID (v) and the token (t) as parameters to get_video. The fmt parameter specifies the quality video you want, none being low, 18 being high, and 22 being HD. Using the get_headers function, we should be returned a 303 response code with the location header set to the video location. I can't guarantee that this is always the case, but it hasn't failed me yet.

From here, you can do with the returned URL as you please. You can use file_get_contents or fsockopen - my favorite - to download the stream, load it into your flash video player or whatever you want. I hope you found this little guide useful. If you run into any problems with the above code, please leave a comment below and I'd be happy to help. Cheers!