Internal: Add setting to limit number of same e-mails - refs #5112

public/main/auth/inscription.php

@@ -288,6 +288,15 @@
 
     $form->addEmailRule('email');
 
+    $form->addRule(
+        'email',
+        get_lang('This e-mail address has already been used by the maximum number of allowed accounts. Please use another.'),
+        'callback',
+        function ($email) {
+            return !api_email_reached_registration_limit($email);
+        }
+    );
+
     // USERNAME
     if ('true' != api_get_setting('login_is_email')) {
         $form->addText(

public/main/inc/lib/api.lib.php

@@ -7577,3 +7577,31 @@ function api_calculate_increment_percent(int $newValue, int $oldValue): string
     }
     return $result;
 }
+
+/**
+ * Checks whether the number of accounts using the given email has reached the configured limit.
+ *
+ * @param string $email The email address to check.
+ *
+ * @return bool True if limit has been reached, false otherwise.
+ */
+function api_email_reached_registration_limit(string $email): bool
+{
+    $limit = (int) api_get_setting('platform.hosting_limit_identical_email');
+
+    if ($limit <= 0 || empty($email)) {
+        return false; // No limit or invalid email
+    }
+
+    $sql = "SELECT COUNT(*) FROM user WHERE email = '".Database::escape_string($email)."'";
+    $result = Database::query($sql);
+
+    if (!$result) {
+        return false;
+    }
+
+    $count = (int) $result->fetchOne();
+
+    return $count >= $limit;
+}
+

src/CoreBundle/DataFixtures/SettingsCurrentFixtures.php

@@ -2002,6 +2002,11 @@ public static function getNewConfigurationSettings(): array
                 ],
             ],
             'platform' => [
+                [
+                    'name' => 'hosting_limit_identical_email',
+                    'title' => 'Limit identical email usage',
+                    'comment' => 'Maximum number of accounts allowed to share the same e-mail address. Set to 0 to disable this limit.',
+                ],
                 [
                     'name' => 'allow_double_validation_in_registration',
                     'title' => 'Double validation for registration process',

src/CoreBundle/Settings/PlatformSettingsSchema.php

@@ -93,6 +93,7 @@ public function buildSettings(AbstractSettingsBuilder $builder): void
                     'redirect_index_to_url_for_logged_users' => '',
                     'default_menu_entry_for_course_or_session' => 'my_courses',
                     'notification_event' => 'false',
+                    'hosting_limit_identical_email' => '0',
                 ]
             )
             ->setTransformer(
@@ -282,6 +283,14 @@ public function buildForm(FormBuilderInterface $builder): void
                 ]
             )
             ->add('notification_event', YesNoType::class)
+            ->add(
+                'hosting_limit_identical_email',
+                TextType::class,
+                [
+                    'label' => 'Limit identical emails',
+                    'help' => 'Maximum number of accounts allowed with the same email. Set to 0 to disable limit.'
+                ]
+            )
         ;
 
         $this->updateFormFieldsFromSettingsInfo($builder);