diff --git a/main/coursecopy/import_backup.php b/main/coursecopy/import_backup.php
index 1c328a8654..70de723487 100755
--- a/main/coursecopy/import_backup.php
+++ b/main/coursecopy/import_backup.php
@@ -60,7 +60,9 @@ if (Security::check_token('post') && (
     Security::clear_token();
 
     $error = false;
-    if (isset($_POST['action']) && $_POST['action'] == 'course_select_form') {
+    if (isset($_POST['action']) &&
+        $_POST['action'] == 'course_select_form'
+    ) {
         // Partial backup here we recover the documents posted
         // This gets $_POST['course']. Beware that when using Suhosin,
         // the post.max_value_length limit might get in the way of the
@@ -282,7 +284,6 @@ if (Security::check_token('post') && (
     $token = Security::get_token();
     $form->addElement('hidden', 'sec_token');
     $form->setConstants(array('sec_token' => $token));
-
     $form->display();
 }
 
diff --git a/main/inc/lib/groupmanager.lib.php b/main/inc/lib/groupmanager.lib.php
index 6cef47308d..eceff54eb0 100755
--- a/main/inc/lib/groupmanager.lib.php
+++ b/main/inc/lib/groupmanager.lib.php
@@ -1526,7 +1526,7 @@ class GroupManager
                 }
             }
 
-            $result = self::number_of_students($group_id) < self:: maximum_number_of_students($groupIid);
+            $result = self::number_of_students($group_id) < self::maximum_number_of_students($groupIid);
 
             if ($result == false) {
                 return false;
@@ -1657,15 +1657,15 @@ class GroupManager
     public static function subscribe_users($user_ids, $groupInfo, $course_id = null)
     {
         $user_ids = is_array($user_ids) ? $user_ids : array($user_ids);
-        $course_id = isset($course_id) && !empty($course_id) ? intval($course_id) : api_get_course_int_id();
+        $course_id = empty($course_id) ? api_get_course_int_id() : (int) $course_id;
         $group_id = $groupInfo['id'];
 
-        $table_group_user = Database::get_course_table(TABLE_GROUP_USER);
+        $table = Database::get_course_table(TABLE_GROUP_USER);
         if (!empty($user_ids)) {
             foreach ($user_ids as $user_id) {
                 if (self::can_user_subscribe($user_id, $groupInfo)) {
                     $user_id = intval($user_id);
-                    $sql = "INSERT INTO ".$table_group_user." (c_id, user_id, group_id)
+                    $sql = "INSERT INTO ".$table." (c_id, user_id, group_id)
                             VALUES ('$course_id', '".$user_id."', '".$group_id."')";
                     Database::query($sql);
                 }
diff --git a/main/inc/lib/plugin.class.php b/main/inc/lib/plugin.class.php
index af19042e05..39edbbcaa8 100755
--- a/main/inc/lib/plugin.class.php
+++ b/main/inc/lib/plugin.class.php
@@ -364,15 +364,19 @@ class Plugin
         // Check whether the language strings for the plugin have already been
         // loaded. If so, no need to load them again.
         if (is_null($this->strings)) {
-            global $language_interface;
+            $language_interface = api_get_interface_language();
             $root = api_get_path(SYS_PLUGIN_PATH);
             $plugin_name = $this->get_name();
 
             $interfaceLanguageId = api_get_language_id($language_interface);
+            if (empty($interfaceLanguageId)) {
+                $language_interface = api_get_setting('platformLanguage');
+                $interfaceLanguageId = api_get_language_id($language_interface);
+            }
             $interfaceLanguageInfo = api_get_language_info($interfaceLanguageId);
             $languageParentId = !empty($interfaceLanguageInfo['parent_id']) ? (int) $interfaceLanguageInfo['parent_id'] : 0;
 
-            //1. Loading english if exists
+            // 1. Loading english if exists
             $english_path = $root.$plugin_name."/lang/english.php";
 
             if (is_readable($english_path)) {
@@ -405,7 +409,6 @@ class Plugin
                 }
             }
         }
-
         if (isset($this->strings[$name])) {
             return $this->strings[$name];
         }