In PHP, what are the key considerations when sending bulk emails using Bcc, and how can the risk of sending duplicate emails to recipients be mitigated?

When sending bulk emails using Bcc in PHP, the key consideration is to ensure that each recipient receives only one email to avoid duplicate emails. To mitigate this risk, you can keep track of the recipients' email addresses in an array and check before sending each email to avoid duplicates.

$recipients = array(); // Array to store email addresses

// Loop through your list of recipients
foreach ($recipientsList as $recipient) {
    // Check if the recipient's email address is not in the array
    if (!in_array($recipient, $recipients)) {
        // Send the email
        // Add the recipient's email address to the array
        $recipients[] = $recipient;
    }
}