Wordpress: inserting author image/avatar as og:image in head

Question

In a post template I'm using a little code to show the author's image/avatar instead of a featured image.

<?php if ( $logo = get_avatar( get_the_author_meta( 'user_email' ), 200 ) ) : echo $logo; ?>

all well.. the author's logo is there But now, as I finishing the project, I would like to add 'og:image' metas in the I hoped to use a variation of this code in the function.php, but that does not work at all.

Now I have this:

add_action('wp_head', 'add_meta_tags',2);
function add_meta_tags(){

global $post;
$author_id = get_post_field('post_author' , $post->ID);
$ogimg  = get_avatar_url($author_id->ID, array("size"=>400 )) ;
if( is_single() ) {
    echo '<meta property="og:image" content="'. $ogimg  .'" />';
    }
}

$author_id gives the ID of the author, but I don't get the avatar of the author.

Answer 1

Couldn't figure out how to use the get_avatar_url function, but found a workaround by extracting the src value from the couple img tag like this:

add_action('wp_head', 'add_meta_tags',1);

function add_meta_tags() {
    global $post;
    $author_id = get_post_field('post_author' , $post->ID);
    $rawimg  = get_avatar($author_id, 800) ;
    $doc = new DOMDocument();
    $doc->loadHTML($rawimg);
    $imageTags = $doc->getElementsByTagName('img');

    foreach($imageTags as $tag) {
        $ogimg = $tag->getAttribute('src');

        echo '<meta property="og:image" content="'.$ogimg  .'" />';
        echo '<meta name="twitter:image" content="'. $ogimg  .'" />';
    }
}