Add option to fetch open graph data from html string

[vedmant]

In my case I fetch page html for further use (searching for other data) but also need to get open graph data, I could use this package if it allowed to pass html string instead of url.

[shweshi]

@vedmant Great suggestion. If you are up to take this up, feel free to open a PR. We can add one more function something like OpenGraph::fetchFromHtml($html) that will accept html and return OG data. This should be easy.

    public function fetchFromHtml($html, $allMeta = null, $lang = null, $options = LIBXML_NOWARNING | LIBXML_NOERROR, $userAgent = 'Curl')
    {
        /**
         * parsing starts here:.
         */
        $doc = new DOMDocument();

        $libxml_previous_state = libxml_use_internal_errors(true);
        $doc->loadHTML('<?xml encoding="utf-8" ?>'.$html, $options);
        //catch possible errors due to empty or malformed HTML
        if ($options > 0 && ($options & (LIBXML_NOWARNING | LIBXML_NOERROR)) == 0) {
            Log::warning(libxml_get_errors());
        }
        libxml_clear_errors();
        // restore previous state
        libxml_use_internal_errors($libxml_previous_state);

        $tags = $doc->getElementsByTagName('meta');
        $metadata = [];
        foreach ($tags as $tag) {
            $metaproperty = ($tag->hasAttribute('property')) ? $tag->getAttribute('property') : $tag->getAttribute('name');
            if (!$allMeta && $metaproperty && strpos($tag->getAttribute('property'), 'og:') === 0) {
                $key = strtr(substr($metaproperty, 3), '-', '_');
                $value = $this->get_meta_value($tag);
            }
            if ($allMeta && $metaproperty) {
                $key = (strpos($metaproperty, 'og:') === 0) ? strtr(substr($metaproperty, 3), '-', '_') : $metaproperty;
                $value = $this->get_meta_value($tag);
            }
            if (!empty($key)) {
                $metadata[$key] = $value;
            }
            /*
             * Verify image url
             */
            if (isset($metadata['image'])) {
                $isValidImageUrl = $this->verify_image_url($metadata['image']);
                if (!$isValidImageUrl) {
                    $metadata['image'] = '';
                }
            }
        }

        return $metadata;
    }

It can reuse the same functions used by fetch method.