RobinBoers/sub.php

## sub.php
<?php

#
# Sub—a simple email subscription service for my blog.
#

$API_HOST = "https://api.geheimesite.nl";
$API_ROOT = "/sub";
$TOKEN = "../token.txt";
$LIST = "../subscribers.csv";
$PUBLIC_EMAIL = "noreply@roblog.nl";
$PRIVATE_EMAIL = "webmaster@roblog.nl";

if(!file_exists($LIST)) {
  touch($LIST);
}

// Send an email for double opt-in before subscribing.
if(isset($_POST['action']) && $_POST['action'] === "new") {
  if(!isset($_POST['planet'])) {
    header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
    echo "Missing 'planet' parameter.";
    exit;
  }

  if($_POST['planet'] === "Moon" || $_POST['planet'] === "SagittariusA") {
    header($_SERVER["SERVER_PROTOCOL"] . " 418 I'm a teapot");
    echo "That's not a planet, you nitwit!";
    exit;
  }

  if($_POST['planet'] !== "Earth") {
    header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
    echo "Sorry, I don't allow aliens to spy on me via my email subscription service.";
    exit;
  }

  if(!isset($_POST['email'])) {
    header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
    echo "Missing 'email' parameter.";
    exit;
  }

  send_confirmation_email($_POST['email']);
  render_next_steps_message();
  exit;
}

function send_confirmation_email($to) {
  global $API_HOST, $API_ROOT, $PUBLIC_EMAIL;
  $link = $API_HOST . $API_ROOT . "?action=confirm&email=" . $to;

  $message = "Hi. You entered your email in the subscribe form for my blog. Thank you for subscribing, it means a lot to me. It's nice to know someone is interested in what I write. To confirm your subscription, visit the link below: " . "\n\r" .  $link . "\n\r\n\r" .  "I always double check the email addresses entered in my form, because I know there's a lot of nasty bots on the Web--hence this confirmation email. I sincerely apologize if you get this email without actually trying to subscribe; a bot must have come through my (pretty bad) filtering." . "\n\r\n\r" . "Again, thank you for subscribing. If you change your mind later, just send me an email and I'll remove you from the list." . "\n\r\n\r" . "Bye," . "\n\r" . "Robin";

  $subject = "Subscribing to my blog";
  $message = wordwrap($message, 70, "\r\n");
  $headers = "From: " . $PUBLIC_EMAIL;

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

function render_next_steps_message() {
  ?>
    <!DOCTYPE html>
    <link rel="stylesheet" href="https://roblog.nl/main.css" />

    <p>Hi, I just want to make sure the email address you provided is actually yours. No need to worry, I do this for all email addresses.</p>
    <p>Please check your email :)</p>
  <?php
}

// Confirm a subscription and add subscriber to list.
if(isset($_GET['action']) && $_GET['action'] === "confirm") {
  if(!isset($_GET['email'])) {
    header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
    echo "Missing 'email' parameter.";
    exit;
  }

  if(!already_subscribed($_GET['email'])) {
    add_to_list($_GET['email']);
    render_success_message();
    hooray($_GET['email']);
  } else {
    render_already_message();
  }

  exit;
}

function already_subscribed($subscriber) {
  global $LIST;
  $subscribers = file_get_contents($LIST);
  return str_contains($subscribers, $subscriber);
}

function add_to_list($email) {
  global $LIST;

  $handle = fopen($LIST, "a+");
  fputcsv($handle, [$email]);
  fclose($handle);
}

function render_success_message() {
  ?>
    <!DOCTYPE html>
    <link rel="stylesheet" href="https://roblog.nl/main.css" />

    <p>You're now subscribed to my blog. Whenever I post something new, you'll automatically get an email.</p>
    <p>Again, thanks for subscribing; it means a lot to me. It's nice to know someone reads my posts.</p>
    <p>If you ever change your mind, just send me an email and I'll remove you from the list. My contact details are on the homepage. No hard feelings :)</p>

    <p><a href="https://roblog.nl">Back to my site 🡢</a></p>
  <?php
}

function render_already_message() {
  ?>
    <!DOCTYPE html>
    <link rel="stylesheet" href="https://roblog.nl/main.css" />

    <p>You were already subscribed. I appreciate your enthusiasm tho :D</p>
    <p><a href="https://roblog.nl">Back to my site 🡢</a></p>
  <?php
}

function hooray($subscriber) {
  global $PUBLIC_EMAIL, $PRIVATE_EMAIL;

  $message = "<" . $subscriber . "> subscribed to your blog; I guess you're not that unpopular after all (yay!)";

  $subject = "Hooray! New subscriber: <" . $subscriber . ">";
  $message = wordwrap($message, 70, "\r\n");
  $headers = "From: " . $PUBLIC_EMAIL;

  mail($PRIVATE_EMAIL, $subject, $message, $headers);
}

// Serve list.
if($_GET['action'] === "download") {
  global $LIST, $TOKEN;

  if($_GET['token'] !== file_get_contents($TOKEN)) {
    header($_SERVER["SERVER_PROTOCOL"] . " 401 Unauthorized");
    echo "Sowwy, can't let you do that... ";
    echo "I'm afraid it would severly breach the GDPR :(";
    exit;
  }

  header('Content-Type: text/csv');
  echo file_get_contents($LIST);
  exit;
}

function render_generic_homepage() {
  ?>
    <!DOCTYPE html>
    <link rel="stylesheet" href="https://roblog.nl/main.css" />

    <h1>Sub<small>—a simple email subscription service for my blog.</small></h1>
    <p><a href="https://roblog.nl/rss#anyway">Wanna subscribe?</a></p>
  <?php
}

render_generic_homepage();
	<?php

	#
	# Sub—a simple email subscription service for my blog.
	#

	$API_HOST = "https://api.geheimesite.nl";
	$API_ROOT = "/sub";
	$TOKEN = "../token.txt";
	$LIST = "../subscribers.csv";
	$PUBLIC_EMAIL = "noreply@roblog.nl";
	$PRIVATE_EMAIL = "webmaster@roblog.nl";

	if(!file_exists($LIST)) {
	touch($LIST);
	}

	// Send an email for double opt-in before subscribing.
	if(isset($_POST['action']) && $_POST['action'] === "new") {
	if(!isset($_POST['planet'])) {
	header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
	echo "Missing 'planet' parameter.";
	exit;
	}

	if($_POST['planet'] === "Moon" \|\| $_POST['planet'] === "SagittariusA") {
	header($_SERVER["SERVER_PROTOCOL"] . " 418 I'm a teapot");
	echo "That's not a planet, you nitwit!";
	exit;
	}

	if($_POST['planet'] !== "Earth") {
	header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
	echo "Sorry, I don't allow aliens to spy on me via my email subscription service.";
	exit;
	}

	if(!isset($_POST['email'])) {
	header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
	echo "Missing 'email' parameter.";
	exit;
	}

	send_confirmation_email($_POST['email']);
	render_next_steps_message();
	exit;
	}

	function send_confirmation_email($to) {
	global $API_HOST, $API_ROOT, $PUBLIC_EMAIL;
	$link = $API_HOST . $API_ROOT . "?action=confirm&email=" . $to;

	$message = "Hi. You entered your email in the subscribe form for my blog. Thank you for subscribing, it means a lot to me. It's nice to know someone is interested in what I write. To confirm your subscription, visit the link below: " . "\n\r" . $link . "\n\r\n\r" . "I always double check the email addresses entered in my form, because I know there's a lot of nasty bots on the Web--hence this confirmation email. I sincerely apologize if you get this email without actually trying to subscribe; a bot must have come through my (pretty bad) filtering." . "\n\r\n\r" . "Again, thank you for subscribing. If you change your mind later, just send me an email and I'll remove you from the list." . "\n\r\n\r" . "Bye," . "\n\r" . "Robin";

	$subject = "Subscribing to my blog";
	$message = wordwrap($message, 70, "\r\n");
	$headers = "From: " . $PUBLIC_EMAIL;

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

	function render_next_steps_message() {
	?>
	<!DOCTYPE html>
	<link rel="stylesheet" href="https://roblog.nl/main.css" />

	<p>Hi, I just want to make sure the email address you provided is actually yours. No need to worry, I do this for all email addresses.</p>
	<p>Please check your email :)</p>
	<?php
	}

	// Confirm a subscription and add subscriber to list.
	if(isset($_GET['action']) && $_GET['action'] === "confirm") {
	if(!isset($_GET['email'])) {
	header($_SERVER["SERVER_PROTOCOL"] . " 400 Bad Request");
	echo "Missing 'email' parameter.";
	exit;
	}

	if(!already_subscribed($_GET['email'])) {
	add_to_list($_GET['email']);
	render_success_message();
	hooray($_GET['email']);
	} else {
	render_already_message();
	}

	exit;
	}

	function already_subscribed($subscriber) {
	global $LIST;
	$subscribers = file_get_contents($LIST);
	return str_contains($subscribers, $subscriber);
	}

	function add_to_list($email) {
	global $LIST;

	$handle = fopen($LIST, "a+");
	fputcsv($handle, [$email]);
	fclose($handle);
	}

	function render_success_message() {
	?>
	<!DOCTYPE html>
	<link rel="stylesheet" href="https://roblog.nl/main.css" />

	<p>You're now subscribed to my blog. Whenever I post something new, you'll automatically get an email.</p>
	<p>Again, thanks for subscribing; it means a lot to me. It's nice to know someone reads my posts.</p>
	<p>If you ever change your mind, just send me an email and I'll remove you from the list. My contact details are on the homepage. No hard feelings :)</p>

	<p><a href="https://roblog.nl">Back to my site 🡢</a></p>
	<?php
	}

	function render_already_message() {
	?>
	<!DOCTYPE html>
	<link rel="stylesheet" href="https://roblog.nl/main.css" />

	<p>You were already subscribed. I appreciate your enthusiasm tho :D</p>
	<p><a href="https://roblog.nl">Back to my site 🡢</a></p>
	<?php
	}

	function hooray($subscriber) {
	global $PUBLIC_EMAIL, $PRIVATE_EMAIL;

	$message = "<" . $subscriber . "> subscribed to your blog; I guess you're not that unpopular after all (yay!)";

	$subject = "Hooray! New subscriber: <" . $subscriber . ">";
	$message = wordwrap($message, 70, "\r\n");
	$headers = "From: " . $PUBLIC_EMAIL;

	mail($PRIVATE_EMAIL, $subject, $message, $headers);
	}

	// Serve list.
	if($_GET['action'] === "download") {
	global $LIST, $TOKEN;

	if($_GET['token'] !== file_get_contents($TOKEN)) {
	header($_SERVER["SERVER_PROTOCOL"] . " 401 Unauthorized");
	echo "Sowwy, can't let you do that... ";
	echo "I'm afraid it would severly breach the GDPR :(";
	exit;
	}

	header('Content-Type: text/csv');
	echo file_get_contents($LIST);
	exit;
	}

	function render_generic_homepage() {
	?>
	<!DOCTYPE html>
	<link rel="stylesheet" href="https://roblog.nl/main.css" />

	<h1>Sub<small>—a simple email subscription service for my blog.</small></h1>
	<p><a href="https://roblog.nl/rss#anyway">Wanna subscribe?</a></p>
	<?php
	}

	render_generic_homepage();