在php回声中转义html标签

Question

I have an AJAX contact form and within the success message i would like to add html tags however when i do, it prints the tags so it shows as...

  <p>Thank You! You are unsubscribed.</p>

how can i amend the following?

    if (mail($recipient, $subject, $email_content, $email_headers)) {
        http_response_code(200);
        echo '<p>Thank You! You are unsubscribed.</p>';
    } else {
        http_response_code(500);
        echo "Oops! Something went wrong and we couldn't send your message.";
    }

it doesnt seem as easy as this How to echo in PHP, html tags

and i can't integrate document.write