Facebook Open Graph Protocol Meta Plugin

fb-og-meta.php

<?php
/*
Plugin Name: Facebook Open Graph Protocol Meta
Plugin URI: http://blogan.net/blog/
Description: Adds Facebook Open Graph Protocol metadata to header on single posts. Requires <a href="http://justintadlock.com/archives/2008/05/27/get-the-image-wordpress-plugin">get-the-image</a> plugin developed by <a href="http://justintadlock.com/">Justin Tadlock</a>.
Version: 0.7
Author: Brent Logan
Author URI: http://blogan.net
License: GPL2
*/

/*
 * [get_the_link] (http://www.turingtarpit.com/2009/03/get-the-image-link/) by [Chandima Cumaranatunge] (http://www.turingtarpit.com).
 */

function get_the_link($args = array()) {
	if (function_exists('get_the_image')) {
		$args = wp_parse_args($args);
		$args['echo'] = false; // prevent echo output

		$imageElement = get_the_image($args);
		$pattern = '/src=([\'"])?(.*?)\\1/i';
		preg_match($pattern, $imageElement, $matches);

		return $matches[2];
	} else {
		return '<!-- Install and activate "Get the Image" plugin first. -->';
	}
}

function fb_ogp_meta() {
	if ( is_single() || is_page() ) { ?>
		<meta property="og:title" content="<?php echo trim(wp_title(' ',false)); ?>" />
		<meta property="og:type" content="article" />
		<meta property="og:locale" content="en_US" />
		<meta property="og:url" content="<?php echo get_permalink(); ?>" />
		<meta property="og:image" content="<?php echo get_the_link( array( 'default_image' => 'http://www.blogan.net/blog/wp-content/uploads/2011/01/avatar2010-tall.png', 'size' => 'medium', 'image_scan' => true ) ); ?>" />
		<meta property="og:site_name" content=" <?php bloginfo('name'); ?>" />
		<meta property="fb:admins" content="500024518" />
		<?php global $post;
		if (is_single()) {
			$fb_ogp_excerpt = esc_html( strip_tags( get_the_excerpt($post->ID) ) );
			echo '<meta property="og:description" content="'; echo $fb_ogp_excerpt; echo '" />' . PHP_EOL;
		}

	} elseif ( is_home() ) { ?>

		<meta property="og:title" content="<?php bloginfo('name'); ?>" />
		<meta property="og:type" content="blog" />
		<meta property="og:locale" content="en_US" />
		<meta property="og:url" content="<?php bloginfo('url'); ?>" />
		<meta property="og:image" content="http://www.blogan.net/blog/wp-content/uploads/2011/01/avatar2010-tall.png" />
		<meta property="og:site_name" content="<?php bloginfo('name'); ?>" />
		<meta property="fb:admins" content="500024518" />
		<meta property="og:description" content="I\'m Brent Logan and I\'ve been here since late 2004, writing about family, food, and fun." />

	<?php }
}

add_action('wp_head', 'fb_ogp_meta');

?>

get_the_link by Chandima Cumaranatunge.