How can HTML newsletters be sent using PHP?

To send HTML newsletters using PHP, you can use the PHP `mail()` function to send emails with HTML content. You need to set the appropriate headers in the email to indicate that the content is HTML. Additionally, you can use PHP libraries like PHPMailer or Swift Mailer for more advanced email sending capabilities.

$to = 'recipient@example.com';
$subject = 'HTML Newsletter';
$message = '<html><body><h1>Hello, this is an HTML newsletter!</h1></body></html>';
$headers = "MIME-Version: 1.0" . "\r\n";
$headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";
$headers .= 'From: sender@example.com' . "\r\n";

mail($to, $subject, $message, $headers);