name it recent_post.php. Replace URL to your forums with the url, leave the backslash. Upload it to your forum directory.
<?php
// Sets the number of topics to display
$topicnumber = 5;
// Change this to your PHPBB3 path (no trailing slash "/")
$urlPath = "URL to your forums/";
// Database configuration (where your PHPBB3 config.php file is located)
include 'config.php';
// Database connection and error messages
$table_topics = $table_prefix. "topics";
$table_forums = $table_prefix. "forums";
$table_posts = $table_prefix. "posts";
$table_users = $table_prefix. "users";
$link = mysql_connect("$dbhost", "$dbuser", "$dbpasswd") or die("Could not connect");
mysql_select_db("$dbname") or die("Could not select database");
// Main database query
$query = "SELECT t.topic_id, t.topic_title, t.topic_last_post_id, t.forum_id, p.post_id, p.poster_id, p.post_time, u.user_id, u.username
FROM $table_topics t, $table_forums f, $table_posts p, $table_users u
WHERE t.topic_id = p.topic_id AND
f.forum_id = t.forum_id AND
/**********************
***********************
EXCLUDE THESE FORUM IDs (if you have private forums)
***********************
**********************/
t.forum_id != 17 AND
t.forum_id != 19 AND
t.forum_id != 20 AND
/**********************
***********************
END EXCLUSIONS
***********************
**********************/
/* Back to the query... */
t.topic_status <> 2 AND
p.post_id = t.topic_last_post_id AND
p.poster_id = u.user_id
ORDER BY p.post_id DESC LIMIT $topicnumber";
$result = mysql_query($query) or die("Query failed");
while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) {
// HTML parsing
echo "<a href=\"$urlPath/viewtopic.php?f=$row[forum_id]&t=$row[topic_id]&p=$row[post_id]#p$row[post_id]\" class='topic_new'>" .
$row["topic_title"] .
"</a><br /><a href=\"$urlPath/memberlist.php?mode=viewprofile&u=$row[user_id]\">" .
$row["username"] . "</a> on " .
date('M j, Y, g:i a', $row["post_time"]) . "<br /><br />";
}
mysql_free_result($result);
mysql_close($link);
?>
<?php include("forums/latest_post.php"); ?>