Get Author's name outside Loop in WordPress

Get Author's name outside Loop in WordPress.php

<?php
    global $post;
    $author_id=$post->post_author;
?>
     
<?php
/* You can also use one of these instead:
  - nickname
  - user_nicename
  - display_name
  - first_name
  - last_name
*/
     
  if( is_single() ) {
    the_author_meta( 'nickname', $author_id );
  } else {
    echo 'Something else';
  }
?>
     
     
use it in your header:
     
<?php global $post; $author_id=$post->post_author; ?>
<meta name="author" content="<?php if(is_single()) { the_author_meta( 'nickname', $author_id ); } else { echo 'Something else'; } ?>">