以下是使用正则表达式从URL提取youtube ID的示例函数：

/**
 * get youtube video ID from URL
 *
 * @param string $url
 * @return string Youtube video id or FALSE if none found. 
 */
function youtube_id_from_url($url) {
    $pattern = 
        '%^# Match any youtube URL
        (?:https?://)?  # Optional scheme. Either http or https
        (?:www\.)?      # Optional www subdomain
        (?:             # Group host alternatives
          youtu\.be/    # Either youtu.be,
        | youtube\.com  # or youtube.com
          (?:           # Group path alternatives
            /embed/     # Either /embed/
          | /v/         # or /v/
          | /watch\?v=  # or /watch\?v=
          )             # End path alternatives.
        )               # End host alternatives.
        ([\w-]{10,12})  # Allow 10-12 for 11 char youtube id.
        $%x'
        ;
    $result = preg_match($pattern, $url, $matches);
    if ($result) {
        return $matches[1];
    }
    return false;
}

echo youtube_id_from_url('http://youtu.be/NLqAF9hrVbY'); # NLqAF9hrVbY

它不是您要查找的API的直接来源，但可能会有所帮助。Youtube有一项固定服务：

$url = 'http://youtu.be/NLqAF9hrVbY';
var_dump(json_decode(file_get_contents(sprintf('http://www.youtube.com/oembed?url=%s&format=json', urlencode($url)))));

其中提供了有关URL的更多元信息：

object(stdClass)#1 (13) {
  ["provider_url"]=>
  string(23) "http://www.youtube.com/"
  ["title"]=>
  string(63) "Hang Gliding: 3 Flights in 8 Days at Northside Point of the Mtn"
  ["html"]=>
  string(411) "<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/NLqAF9hrVbY?version=3"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/NLqAF9hrVbY?version=3" type="application/x-shockwave-flash" width="425" height="344" allowscriptaccess="always" allowfullscreen="true"></embed></object>"
  ["author_name"]=>
  string(11) "widgewunner"
  ["height"]=>
  int(344)
  ["thumbnail_width"]=>
  int(480)
  ["width"]=>
  int(425)
  ["version"]=>
  string(3) "1.0"
  ["author_url"]=>
  string(39) "http://www.youtube.com/user/widgewunner"
  ["provider_name"]=>
  string(7) "YouTube"
  ["thumbnail_url"]=>
  string(48) "http://i3.ytimg.com/vi/NLqAF9hrVbY/hqdefault.jpg"
  ["type"]=>
  string(5) "video"
  ["thumbnail_height"]=>
  int(360)
}

但是ID并不是响应的直接部分。但是，它可能包含您要查找的信息，并且可能对验证youtube URL有用。