How can the user prevent duplicate email addresses from receiving multiple newsletters in their PHP script?

To prevent duplicate email addresses from receiving multiple newsletters in a PHP script, you can first check if the email address already exists in your database before adding it again. This can be done by querying the database to see if the email address is already present. If it is, then you can skip adding it again to avoid duplicates. 

// Connect to your database
$pdo = new PDO('mysql:host=localhost;dbname=your_database', 'username', 'password');

// Check if the email address already exists in the database
$email = $_POST['email'];
$stmt = $pdo->prepare("SELECT COUNT(*) FROM subscribers WHERE email = :email");
$stmt->bindParam(':email', $email);
$stmt->execute();
$count = $stmt->fetchColumn();

// If the email address doesn't exist, add it to the subscribers table
if($count == 0) {
    $stmt = $pdo->prepare("INSERT INTO subscribers (email) VALUES (:email)");
    $stmt->bindParam(':email', $email);
    $stmt->execute();
    echo "Successfully subscribed!";
} else {
    echo "Email address already subscribed!";
}

Keywords

PHP email addresses newsletters duplicate prevention validation

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