<?php $post_author = $this->get('post_author'); ?>
<?php if ($post_author) : ?>
    <div class="amp-wp-meta amp-wp-byline">
        <span class="amp-wp-author author vcard"><?php echo pixwell_translate( 'by' ) . ' '; ?><?php echo esc_html( $post_author->display_name ); ?></span>
    </div>
<?php endif;