WordPress - Use Gravatar image as WordPress favicon

functions.php

<?php
// Add the following code in theme's functions.php file to use Gravatar image as favicon (16x16 favicon.ico)
function dcg_gravatar_favicon() {
    // Replace email here
    $GetEmailHash = md5(strtolower(trim('[email protected]')));
?>
<link rel="shortcut icon" href="<?php echo 'http://www.gravatar.com/avatar/' . $GetEmailHash . '?s=16;'; ?>" type="image/x-icon" />
<?php
}
add_action('wp_head', 'dcg_gravatar_favicon');