A simple multipurpose php youtube url parser, this was used for specific needs so it is not really generic.

YoutubeUrlParser.php

<?php

class YoutubeUrlParser
{
    const REGULAR_URL_FORMAT = '/^https?:\/\/(www\.)?youtube\.com\/watch/';
    const EMBEDDED_URL_FORMAT = '/^https?:\/\/(www\.)?youtube\.com\/embed/';
    const SHARE_URL_FORMAT = '/^https?:\/\/(www\.)?youtu\.be\//';

    private $originalUrl;
    private $videoId;

    public function __construct($url)
    {
        $this->originalUrl = $url;
    }

    public function videoId()
    {
        if($this->videoId) return $this->videoId;

        $urlParts = parse_url($this->originalUrl);
        $urlQuery = [];
        $queryStr = array_get($urlParts, 'query', '');
        $pathUrl = array_get($urlParts, 'path', '');

        parse_str($queryStr, $urlQuery);

        if($this->isRegular()){
            return $this->videoId = $urlQuery['v'];
        }

        if($this->isShareOrEmbedded()){
            $splittedPath = explode('/', $pathUrl);
            return $this->videoId = end($splittedPath);
        }
    }

    public function isValid(){
        return $this->isRegular() || $this->isShareOrEmbedded();
    }

    private function isRegular()
    {
        return preg_match(self::REGULAR_URL_FORMAT, $this->originalUrl);
    }

    private function isShareOrEmbedded()
    {
        return preg_match(self::SHARE_URL_FORMAT, $this->originalUrl) 
            || preg_match(self::EMBEDDED_URL_FORMAT, $this->originalUrl);
    }

    public function thumbnailUrl()
    {
        return 'https://img.youtube.com/vi/' . $this->videoId() . '/hqdefault.jpg';
    }

    public function embeddedUrl()
    {
        return 'http://www.youtube.com/embed/' . $this->videoId();
    }

    public function url()
    {
        return 'https://youtu.be/'. $this->videoId();
    }

    public function __toString()
    {
        return $this->embeddedUrl();
    }
}