Count customers email domain occurences from Magento orders

providers.php

<?php

require_once('app/Mage.php');
umask(0);
Mage::app();

$emails = array();
$orders = Mage::getModel('sales/order')->getCollection();
foreach ($orders as $order) {
    $emails[] = $order->getCustomerEmail();
}

$domains = array();

foreach ($emails as $email) {
    $domain = substr(strrchr($email, "@"), 1);
    $domains[$email] = $domain;
}

$total = count($domains);

$occurences = array_count_values($domains);
arsort($occurences);
foreach ($occurences as $domain => $count) {
    $percent = round(($count / $total) * 100, 2);
    echo "$domain ($count) - $percent%<br/>";
}