Are there alternative methods, such as blacklisting, that could be more effective for restricting registration to a specific group of users based on their email addresses?

One alternative method for restricting registration to a specific group of users based on their email addresses is by using whitelisting. This involves creating a list of approved email addresses and only allowing registration for users with email addresses that are on this list. This can be more effective than blacklisting as it only allows a specific group of users to register. 

// Whitelisting email addresses for registration
$allowed_emails = array("user1@example.com", "user2@example.com");

if (in_array($_POST['email'], $allowed_emails)) {
    // Allow registration
    // Your registration code here
} else {
    // Display error message
    echo "Sorry, registration is only allowed for specific email addresses.";
}

Keywords

blacklisting registration specific group email addresses alternative methods

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