WordPress function for Facebook OG meta tags

functions.php

<?php
// put this into your theme's functions.php file
// swap out the default image online 10
// build the facebook og meta tags based on defaults
// or if on a page or post, pull information off that object
function opengraph_tags() {

    // defaults
    $title = get_bloginfo('title');
    $img_src = get_stylesheet_directory_uri() . '/images/your_default_image_here.jpg';
    $excerpt = get_bloginfo('description');
    // for non posts/pages, like /blog, just use the current URL
    $permalink = "http://".$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];

    if(is_single() || is_page()) {

        global $post;
        setup_postdata( $post );

        $title = get_the_title();
        $permalink = get_the_permalink();

        if (has_post_thumbnail($post->ID)) {
            $img_src = wp_get_attachment_image_src(get_post_thumbnail_id($post->ID), 'large')[0];
        }

        $excerpt = get_the_excerpt();

        if ($excerpt) {
            $excerpt = strip_tags($excerpt);
            $excerpt = str_replace("", "'", $excerpt);
        }
    }
    ?>

<meta property="og:title" content="<?= $title; ?>"/>
<meta property="og:description" content="<?= $excerpt; ?>"/>
<meta property="og:type" content="article"/>
<meta property="og:url" content="<?= $permalink; ?>"/>
<meta property="og:site_name" content="<?= get_bloginfo(); ?>"/>
<meta property="og:image" content="<?= $img_src; ?>"/>

<?php
}
add_action('wp_head', 'opengraph_tags', 5);