Horde - Virtual Alias Update

<?php
/**
 * Updating Postfix virtual alias maps from Horde.
 *
 * Horde allows users to have multiple "identities" and email aliases under
 * those identities. When running a personal mail server, it's more than
 * likely that all of those email addresses should be deliverable. This script
 * takes all of the aliases in Horde's database and rewrites the virtual alias
 * maps and domains files using the identities setup in Horde. Additionally,
 * it will only update the files and reload postfix if a file has changed, so
 * it is safe to run as a cron job as often as needed.
 *
 * Note that this script was written for Postfix on CentOS 6.4, and therefore
 * you may need to update the locations of the "postmap" and "service"
 * executables at the end of this script if you use a distribution other than
 * CentOS. If you use a mail server other than postscript, if that mail server
 * has the concept of alias maps/domains, then you may still be able to use
 * this script, however it will need to be modified to use a format specific
 * to that application. You may also need to update the locations of the maps
 * and domains file at the beginning of this script if you have an existing
 * setup with those files in different locations, or if you just want to put
 * these files somewhere else. Additionally, you WILL need to update the MySQL
 * connection information at the beginning of this script with your own.
 *
 * @author     Ryan Petris <ryan@petris.net>
 * @copyright  (c) 2013 Ryan Petris
 * @license    GNU/GPLv3 http://www.gnu.org/licenses/gpl-3.0.html
 */

$db = new PDO("mysql:host=localhost;dbname=horde", "username", "password");
$maps_file = "/etc/postfix/virtual_alias_maps";
$domains_file = "/etc/postfix/virtual_alias_domains";

$stmt = $db->prepare("SELECT * FROM horde_prefs WHERE pref_name = 'identities';");
$stmt->execute();
$prefs = $stmt->fetchAll(PDO::FETCH_ASSOC);

$emails = array();
$email_lines = array();
$domains = array();

if (!count($prefs)) {
    die("Nothing returned from database query!");
}

foreach ($prefs as $pref) {
    if (!array_key_exists($pref["pref_uid"], $emails)) {
        $emails[$pref["pref_uid"]] = array();
    }

    $items = unserialize($pref["pref_value"]);

    foreach ($items as $item) {
        if (!empty($item["from_addr"]) && !in_array($item["from_addr"], $emails[$pref["pref_uid"]])) {
            $emails[$pref["pref_uid"]][] = $item["from_addr"];
        }

        if (array_key_exists("alias_addr", $item)) {
            foreach ($item["alias_addr"] as $alias) {
                if (!empty($alias) && !in_array($alias, $emails[$pref["pref_uid"]])) {
                    $emails[$pref["pref_uid"]][] = $alias;
                }
            }
        }
    }
}

foreach ($emails as $user => $useremails) {
    foreach ($useremails as $email) {
        $email_lines[] = $email . " " . $user;

        $parts = explode('@', $email);

        if ($parts) {
            $domain = $parts[count($parts) - 1];

            if (!in_array($domain, $domains)) {
                $domains[] = $domain;
            }
        }
    }
}

$update = false;

$maps_contents = file_get_contents($maps_file);
$domains_contents = file_get_contents($domains_file);

$maps_contents_new = implode("\n", $email_lines) . "\n";
$domains_contents_new = implode("\n", $domains) . "\n";

if ($maps_contents != $maps_contents_new || $domains_contents != $domains_contents_new) {
    file_put_contents($maps_file, $maps_contents_new);
    file_put_contents($domains_file, $domains_contents_new);

    exec("/usr/sbin/postmap " . $maps_file);
    exec("/sbin/service postfix reload");
}