<?php
define('DB_HOST', 'localhost');
define('DB_NAME', '*****');
define('DB_USERNAME', '****');
define('DB_PASS', '******');
class Newsletter {
    private $db;
    public function __construct() {
        $this->db = new mysqli(DB_HOST, DB_USERNAME, DB_PASS, DB_NAME);
    }
    public function __destruct() {
        $this->db->close();
    }
    public function addEntry($email) {
    }
    private function sendConfirmation($to, $from, $key) {
    }
    public function confirmEmail($key) {
    }
}

public function addEntry($email) {
    $result = false;
    if(!filter_var($email, FILTER_VALIDATE_EMAIL)) return false;
    $email_key = md5(uniqid());
    $sql = 'INSERT INTO
                        service4life_email_list (email, email_key, is_active, date)
            VALUES(?, ?, "false", NOW())';
    $stmt = $this->db->prepare($sql);
    $stmt->bind_param('ss', $email, $email_key);
    $stmt->execute();
    if(!empty($this->db->error)) return false;
    $result = $stmt->insert_id;
    $stmt->close();
    $this->sendConfirmation($email, 'example@example.com', $key);
    return (bool)$result;
}

private function sendConfirmation($to, $from, $key) {
     $subject = 'Newsletter Bestätigung';
     $headers = "From: " . $from . "\r\n";
     $headers .= "Reply-To: ". $from . "\r\n";
     $headers .= "CC: $from \r\n";
     $headers .= "MIME-Version: 1.0\r\n";
     $headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";
     $message = 'Bitte bestätigen Sie Ihre E-Mail-Adresse für den Newsletter mit ';
     $message .= 'folgendem Link: <a  href="http://example.com/includes/confirm-email.php?key='.$key.'">Bestätigung</a>';
     mail($to, $subject, $message, $headers);
 }
public function confirmEmail($key) {
    $sql = 'UPDATE service4life_email_list
            SET is_active = "true"
            WHERE email_key = ?';
    $stmt = $this->db->prepare($sql);
    $stmt->bind_param('s', $key);
    $stmt->execute();
    $result = $stmt->affected_rows;
    $stmt->close();
    return (bool)$result;
}

?>