WordPress: get author info from post id

Solution 1:

I figured it out.

<?php $author_id=$post->post_author; ?>
<img src="<?php the_author_meta( 'avatar' , $author_id ); ?> " width="140" height="140" class="avatar" alt="<?php echo the_author_meta( 'display_name' , $author_id ); ?>" />
<?php the_author_meta( 'user_nicename' , $author_id ); ?> 

Solution 2:

If you want it outside of loop then use the below code.

<?php
$author_id = get_post_field ('post_author', $cause_id);
$display_name = get_the_author_meta( 'display_name' , $author_id ); 
echo $display_name;
?>

Solution 3:

<?php
  $field = 'display_name';
  the_author_meta($field);
?>

Valid values for the $field parameter include:

• admin_color
• aim
• comment_shortcuts
• description
• display_name
• first_name
• ID
• jabber
• last_name
• nickname
• plugins_last_view
• plugins_per_page
• rich_editing
• syntax_highlighting
• user_activation_key
• user_description
• user_email
• user_firstname
• user_lastname
• user_level
• user_login
• user_nicename
• user_pass
• user_registered
• user_status
• user_url
• yim

Solution 4:

**use this code for display Auth Name**

<?php
$auth_id = $post->post_author; 
echo get_the_author_meta( 'display_name', $auth_id ); 
?>