function wpb_author_info_box( $content ) {
  
global $post;
  
// Detect if it is a single post with a post author
if ( is_single() && isset( $post->post_author ) ) {
  
// Get author's display name
$display_name = get_the_author_meta( 'display_name', $post->post_author );
  
// If display name is not available then use nickname as display name
if ( empty( $display_name ) )
$display_name = get_the_author_meta( 'nickname', $post->post_author );
  
// Get author's biographical information or description
$user_description = get_the_author_meta( 'user_description', $post->post_author );
  
// Get author's website URL
$user_website = get_the_author_meta('url', $post->post_author);
  
// Get link to the author archive page
$user_posts = get_author_posts_url( get_the_author_meta( 'ID' , $post->post_author));
  
if ( ! empty( $display_name ) )
  
$author_details = '<p class="author_name">About ' . $display_name . '</p>';
  
if ( ! empty( $user_description ) )
// Author avatar and bio
  
$author_details .= '<p class="author_details">' . get_avatar( get_the_author_meta('user_email') , 90 ) . nl2br( $user_description ). '</p>';
  
$author_details .= '<p class="author_links"><a href="'. $user_posts .'">View all posts by ' . $display_name . '</a>'; 
  
// Check if author has a website in their profile
if ( ! empty( $user_website ) ) {
  
// Display author website link
$author_details .= ' | <a href="' . $user_website .'" target="_blank" rel="nofollow">Website</a></p>';
  
} else {
// if there is no author website then just close the paragraph
$author_details .= '</p>';
}
  
// Pass all this info to post content
$content = $content . '<footer class="author_bio_section" >' . $author_details . '</footer>';
}
return $content;
}
  
// Add our function to the post content filter
add_action( 'the_content', 'wpb_author_info_box' );
  
// Allow HTML in author bio section
remove_filter('pre_user_description', 'wp_filter_kses');