Wordpress the author function waterfall page - php

Question

I am working on a custom blog roll for my website but cannot for the life of me figure out how to print out the author. Here is what I have so far:
<div id="blog_roll">
<?
$args = array('tag__not_in' => '5');
$posts = get_posts($args);
foreach($posts as $post) {
?>
<div class="waterfall">
<div id="waterfall_thumb">
<a href="<?php the_permalink(); ?>">
<?php the_post_thumbnail(); ?>
</a>
</div>
<div id="waterfall_title">
<a href="<?php the_permalink(); ?>">
<?php the_title(); ?>
</a>
</div>
<div id="waterfall_author">
by:<?php the_author();?>on <?php the_time( get_option( 'date_format' ) ); ?>
</div>
<div id="waterfall_exc">
<?php echo apply_filters( 'the_content', $post->post_excerpt ); ?></div>
</div>
<? } ?>
Any help would be greatly appreciated!

Answer 1

The the_author() function works only inside The Loop™. To get an author's details outside the Loop, you can take the author's ID from the $post object and use it with the the_author_meta() function:
… by: <?php the_author_meta('display_name', $post->post_author); ?> …
See the function reference in the WordPress Codex for other available fields.
By the way, the_permalink also works only inside the Loop. You need to use
<?php echo get_permalink($post->ID); ?>

Answer 2

I use this on my wordpress blog
$user_url = get_the_author_meta('user_url', $post->post_author);
$user_name = get_the_author_meta('user_nicename', $post->post_author);
echo '' . ' by ' . $user_name . '';
As the other user mentions, the_author is only available inside the loop, so you need to use the_author_metadata (http://codex.wordpress.org/Function_Reference/the_author_meta)