Email Censorship

<?php
$text = $_GET['text'];
$blacklist = preg_split('/[*\s]+/', $_GET['blacklist'], -1, PREG_SPLIT_NO_EMPTY);

$emailPattern = "/\b([\w+-]+)@([A-Za-z0-9-]+)\.([A-Za-z0-9.-]+)\b/";
if (preg_match_all($emailPattern, $text, $matches)) {
    $fullEmails = $matches[0];
    $domainParts = $matches[3];
    foreach ($fullEmails as $key => $email) {
        $domain = $domainParts[$key];
        $isBlackListed = false;
        if (in_array($email, $blacklist)) {
            $isBlackListed = true;
        } else {
            foreach ($blacklist as $blacklisted) {
                if ($blacklisted[0] == '.' && (strpos($blacklisted, $domain) === 1)
                ) {
                    $isBlackListed = true;
                    break;
                }
            }
        }

        if ($isBlackListed) {
            $replacement = str_repeat('*', strlen($email));
        } else {
            $replacement = '<a href="mailto:' . $email . '">' . $email . '</a>';
        }

        $text = str_replace($email, $replacement, $text);
    }
}
?>

<p><?= $text ?></p>