Wordpress - Get author full name

Try the following:

<?php

$fname = get_the_author_meta('first_name');
$lname = get_the_author_meta('last_name');
$full_name = '';

if( empty($fname)){
    $full_name = $lname;
} elseif( empty( $lname )){
    $full_name = $fname;
} else {
    //both first name and last name are present
    $full_name = "{$fname} {$lname}";
}

echo $full_name;
?>

The get_the_author can directly be used to display the name of the author. There are few settings to be done on the admin for this:

• Under the user settings add make sure you have the first and last name fields filled up.
• After that see for the Display name publicly as options and select whichever format you want the name to be shown.
• Click save and refresh your page.