WP-Plugin: Random Post of the day

<?php
/*
	Random Post of the day by Ahmet Topal, http://ahmet-topal.de/
	Informations: http://basicblogger.de/2009/05/26/wp-plugin-random-post-of-the-day/
 
	This Plugins allows you to show a Random Post of the day anywhere using <?php at_random_post(); ?>
*/
 
function at_random_post() {
	global $wpdb;
 
	// Database select a random Post
	$query = "SELECT id, post_title, post_name FROM $wpdb->posts WHERE ((post_status='publish') AND (post_type = 'post') AND ($wpdb->posts.post_password = '')) ORDER BY RAND() LIMIT 1";
	$randompost = $wpdb->get_results($query);
	$post = $randompost[0];
	$post_title = htmlspecialchars(stripslashes($post->post_title));
	$showpost .= '<a href="' . get_permalink($post->id) . '" title="'. $post_title . '">' . $post_title .'</a>' . "n";
 
	// Add Options to the Database
	add_option('at_random_post', mktime(0,0,0));
	add_option('at_get_random_post', $showpost);
 
	if(time() > get_option('at_random_post')+86400)
	{
		echo $showpost;
 
		// Update Options
		update_option('at_random_post', mktime(0,0,0));
		update_option('at_get_random_post', $showpost);
	}
	else
	{
		$showpostdb = get_option('at_get_random_post');
		echo $showpostdb;
	}
}
?>

<?php at_random_post(); ?>

	// Database select a random Post
	$query = "SELECT id, post_title, post_name FROM $wpdb->posts WHERE ((post_status='publish') AND (post_type = 'post') AND ($wpdb->posts.post_password = '')) ORDER BY RAND() LIMIT 1";
	$randompost = $wpdb->get_results($query);
	$post = $randompost[0];
	$post_title = htmlspecialchars(stripslashes($post->post_title));
	$showpost .= '<a href="' . get_permalink($post->id) . '" title="'. $post_title . '">' . $post_title .'</a>' . "n";

	// Database select a random Post
	$query = "SELECT id, post_title, post_content, post_name FROM $wpdb->posts WHERE ((post_status='publish') AND (post_type = 'post') AND ($wpdb->posts.post_password = '')) ORDER BY RAND() LIMIT 1";
	$randompost = $wpdb->get_results($query);
	$post = $randompost[0];
	$post_title = htmlspecialchars(stripslashes($post->post_title));
	$showpost .= '<a href="' . get_permalink($post->id) . '" title="'. $post_title . '">' . $post_title .'</a>' . "<br />n" .  substr(nl2br($post->post_content), 0,  200) . "...n";