Gravのカスタムショートコードでリンクカードを作る。

LinkcardShortcode.php

<?php
namespace Grav\Plugin\Shortcodes;

use Thunder\Shortcode\Shortcode\ShortcodeInterface;
use Thunder\Shortcode\Shortcode\ProcessedShortcode;

class LinkcardShortcode extends Shortcode {
    public function init() {
        $this->shortcode->getHandlers()->add('site', function(ProcessedShortcode $sc) {
            $url = $sc->getParameter('url');
            $purl = parse_url($url);
            $img = $sc->getParameter('img');
            $content = $sc->getContent();
            $html = null;

            if($url){
                $data = $this->get_ogp($url,$img,$content);
                $img = $data['img'];
                $title = $data['title'];
                $desc = $data['desc'];

                $html = '<blockquote class="link panel panel-default"><a onclick="ga(\'send\',\'event\',\'BlogCard\',\'click\',location.href);" rel="noopener" target="_blank" href="'.$url.'">';
                $html .= '<img class="thumb pull-right" src="'.$img.'" alt="'.$title.'" /><span class="lead text-primary">'.$title.'</span>';
                $html .= '<p>'.$desc.'</p><footer><img class="favicon" src="//www.google.com/s2/favicons?domain_url='.urlencode($url).'" /> '.$purl['host'].'</footer><div class="clearfix"></div></a></blockquote>';
            }
            return $html;
        });
    }

    private function get_ogp($url,$img = null,$title = null){
        $context = stream_context_create(array(
        'http' => array('ignore_errors' => true)
        ));
        $html = file_get_contents($url, false, $context);
        $description = null;
        $thumb = null;

        if($html){
            preg_match('/<title>(.*)<\/title>/',$html,$mt);
            if($mt && $mt[1]){$title = $mt[1];}

            preg_match('/<meta property="og:image" content="http([^\n]*)"/',$html,$mi);
            if($mi && $mi[1]){$thumb = 'http'.$mi[1];}

            preg_match('/<meta name="description" content="([^\n]*)"/',$html,$md);
            if($md && $md[1]){$description = $md[1];}
            else{
                preg_match('/<meta property="og:description" content="([^\n]*)"/',$html,$md);
                if($md && $md[1]){$description = $md[1];}
            }
        }

        if($img){$thumb = $img;}
        elseif(!$thumb){$thumb = '/empty.gif';}
        $data = array(
            'title' => $title,
            'img' => $thumb,
            'desc' => mb_substr($description,0,200)
        );
        return $data;
    }
}