enabling email for registration.

auth.php

@@ -388,6 +388,24 @@ function generateRegistrationCode() {
     return str_pad((string) random_int(0, 999999), 6, '0', STR_PAD_LEFT);
 }
 
+function sendRegistrationVerificationEmail($email, $code) {
+    $email = trim((string) $email);
+    if ($email === '') {
+        return false;
+    }
+
+    $subject = 'Your KaI registration verification code';
+    $message = "Hello,\n\n"
+        . "You requested to create a KaI account.\n"
+        . "Your verification code is: {$code}\n\n"
+        . "Please enter this code on the registration page to complete your account setup.";
+    $headers = "From: " . MAIL_FROM_NAME . " <" . MAIL_FROM . ">\r\n"
+        . "Reply-To: " . MAIL_FROM . "\r\n"
+        . "X-Mailer: PHP/" . phpversion();
+
+    return mail($email, $subject, $message, $headers);
+}
+
 function savePendingRegistration($username, $email, $password, $code) {
     if (session_status() === PHP_SESSION_NONE) {
         session_start();

register.php

@@ -52,11 +52,10 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
                 $errors[] = 'That username or email is already in use.';
             } else {
                 $code = generateRegistrationCode();
-                if (savePendingRegistration($username, $email, $password, $code)) {
+                if (savePendingRegistration($username, $email, $password, $code) && sendRegistrationVerificationEmail($email, $code)) {
                     $message = 'A verification code has been sent to ' . htmlspecialchars($email) . '. Please enter it below.';
-                    $message .= ' (For demo purposes, the code is: ' . htmlspecialchars($code) . ')';
                 } else {
-                    $errors[] = 'Unable to start registration.';
+                    $errors[] = 'Unable to start registration. Please check that your email address is valid and the mail server is configured.';
                 }
             }
         }