Creating Custom WordPress Get Avatar Function

functions.php

add_filter('get_avatar', 'ajtd_get_avatar', 10, 6);
function ajtd_get_avatar($avatar, $id_or_email, $size, $default, $alt) {
    $args['size'] = (int) $size;  

    $url2x = get_avatar_url($id_or_email, array_merge($args, array('size' => $args['size'] * 2)));

    $args = get_avatar_data($id_or_email, $args);

    $url = $args['url']; 

    $class = array('avatar', 'avatar-' . (int) $args['size'], 'photo', 'ajtd-avatar');  

    $avatar = sprintf(
        "<img alt='%s' title='%s' itemprop='image' src='%s' srcset='%s' class='%s' height='%d' width='%d' %s/>",
        esc_attr($alt),
        esc_attr($alt),
        esc_url($url),
        esc_attr("$url2x 2x"),
        esc_attr(join( ' ', $class)),
        (int) $args['height'],
        (int) $args['width'],
        $args['extra_attr']
    );

    return $avatar;
}