I am getting a Like button on my small Wordpress site. Let me make use of the og:image meta-tag from facebook to show the correct image when somebody wants it. I have to include that tag within the mind from the page. To date I've this in single.php:

function fb_image_meta($image) {
    return '<meta property="og:image" content="$image" />';
}

add_action('wp_head', 'fb_image_meta', 10, $image_thumbnail); 

After I consider the supply of articles, The meta tag does not appear.

What shall we be held doing wrong?

Make use of this code in functions.php

function fb_image_meta($image) {
    echo '<meta property="og:image" content="$image" />';
}

add_action('wp_head', 'fb_image_meta', 10, $image_thumbnail);

You need to take proper care of $image_thumbnail - it should be declared before wordpress_mind. If this sounds like a publish thumbnail, you will get it with this particular code (prior to the add_action call):

global $post;
$image_thumbnail = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'large');