koblog/bl-plugins/opengraph/plugin.php

<?php

class pluginOpenGraph extends Plugin
{

	public function init()
	{
		// Fields and default values for the database of this plugin
		$this->dbFields = array(
			'defaultImage' => '',
			'fbAppId' => ''
		);
	}

	public function form()
	{
		global $L;

		$html  = '<div class="alert alert-primary" role="alert">';
		$html .= $this->description();
		$html .= '</div>';

		$html .= '<div>';
		$html .= '<label>' . $L->get('Default image') . '</label>';
		$html .= '<input id="jsdefaultImage" name="defaultImage" type="text" dir="auto" value="' . $this->getValue('defaultImage') . '" placeholder="https://">';
		$html .= '<span class="tip">' . $L->g('set-a-default-image-for-content') . '</span>';
		$html .= '</div>';

		$html .= '<div>';
		$html .= '<label>' . $L->get('Facebook App ID') . '</label>';
		$html .= '<input name="fbAppId" type="text" dir="auto" value="' . $this->getValue('fbAppId') . '" placeholder="App ID">';
		$html .= '<span class="tip">' . $L->g('set-your-facebook-app-id') . '</span>';
		$html .= '</div>';

		return $html;
	}

	public function siteHead()
	{
		global $url;
		global $site;
		global $WHERE_AM_I;
		global $page;
		global $content;

		$og = array(
			'locale'	=> $site->locale(),
			'type'		=> 'website',
			'title'		=> $site->title(),
			'description'	=> $site->description(),
			'url'		=> $site->url(),
			'image'		=> '',
			'siteName'	=> $site->title()
		);

		switch ($WHERE_AM_I) {
				// The user filter by page
			case 'page':
				$og['type']		= 'article';
				$og['title']		= $page->title();
				$og['description']	= $page->description();
				$og['url']		= $page->permalink($absolute = true);
				$og['image'] 		= $page->coverImage($absolute = true);

				$pageContent = $page->content();
				break;

				// The user is in the homepage
			default:
				$pageContent = '';
				if (Text::isNotEmpty($this->getValue('defaultImage'))) {
					$og['image'] = $this->getValue('defaultImage');
				} elseif (isset($content[0])) {
					$og['image'] 	= $content[0]->coverImage($absolute = true);
					$pageContent 	= $content[0]->content();
				}
				break;
		}

		$html  = PHP_EOL . '<!-- Open Graph -->' . PHP_EOL;
		$html .= '<meta property="og:locale" content="' . $og['locale'] . '">' . PHP_EOL;
		$html .= '<meta property="og:type" content="' . $og['type'] . '">' . PHP_EOL;
		$html .= '<meta property="og:title" content="' . $og['title'] . '">' . PHP_EOL;
		$html .= '<meta property="og:description" content="' . $og['description'] . '">' . PHP_EOL;
		$html .= '<meta property="og:url" content="' . $og['url'] . '">' . PHP_EOL;
		$html .= '<meta property="og:site_name" content="' . $og['siteName'] . '">' . PHP_EOL;

		// If the page doesn't have a coverImage try to get an image from the HTML content
		if (empty($og['image'])) {
			// Get the image from the content
			$src = DOM::getFirstImage($pageContent);
			if ($src !== false) {
				$og['image'] = $src;
			} else {
				if (Text::isNotEmpty($this->getValue('defaultImage'))) {
					$og['image'] = $this->getValue('defaultImage');
				}
			}
		}

		$html .= '<meta property="og:image" content="' . $og['image'] . '">' . PHP_EOL;
		if (Text::isNotEmpty($this->getValue('fbAppId'))) {
			$html .= '<meta property="fb:app_id" content="' . $this->getValue('fbAppId') . '">' . PHP_EOL;
		}
		return $html;
	}
}