", "Reply-To: [email protected]", "X-Mailer: PHP/" . PHP_VERSION, "MIME-Version: 1.0", "Content-Type: text/html; charset=UTF-8" ]); mail($to, $subject, $message, $headers);"> ", "Reply-To: [email protected]", "X-Mailer: PHP/" . PHP_VERSION, "MIME-Version: 1.0", "Content-Type: text/html; charset=UTF-8" ]); mail($to, $subject, $message, $headers);"> ", "Reply-To: [email protected]", "X-Mailer: PHP/" . PHP_VERSION, "MIME-Version: 1.0", "Content-Type: text/html; charset=UTF-8" ]); mail($to, $subject, $message, $headers);"> 
<?php
$to      = '[email protected]';
$subject = 'Sending an HTML email using mail() in PHP';
$message = '<html><body><p><b>This paragraph is bold.</b></p><p><i>This text is italic.</i></p></body></html>';

$headers = implode("\\r\\n", [
    "From: John Conde <[email protected]>",
    "Reply-To: [email protected]",
    "X-Mailer: PHP/" . PHP_VERSION,
    "MIME-Version: 1.0",
    "Content-Type: text/html; charset=UTF-8"
]);

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

This is not much different then sending a plain text email. Thet key differences being the content body is structured like an HTML document and there are two additional headers that must be included so the email client knows to trender the email as HTML. They are: