diff --git a/mod/forum/classes/local/entities/forum.php b/mod/forum/classes/local/entities/forum.php
index 4d4808b824b..53cfebdae0f 100644
--- a/mod/forum/classes/local/entities/forum.php
+++ b/mod/forum/classes/local/entities/forum.php
@@ -99,8 +99,8 @@ class forum {
     private $completionreplies;
     /** @var int $completionposts Completion posts */
     private $completionposts;
-    /** @var bool $displaywordcounts Should display word counts in posts */
-    private $displaywordcounts;
+    /** @var bool $displaywordcount Should display word counts in posts */
+    private $displaywordcount;
     /** @var bool $lockdiscussionafter Timestamp after which discussions should be locked */
     private $lockdiscussionafter;
     /** @var int $duedate Timestamp that represents the due date for forum posts */
diff --git a/mod/forum/classes/output/big_search_form.php b/mod/forum/classes/output/big_search_form.php
index 119c9bc6394..42bfdc760f0 100644
--- a/mod/forum/classes/output/big_search_form.php
+++ b/mod/forum/classes/output/big_search_form.php
@@ -59,6 +59,8 @@ class big_search_form implements renderable, templatable {
     public $guestuser;
     /** @var bool Whether the include starredonly checkbox is checked. */
     public $starredonly;
+    /** @var int forum ID. */
+    public $forumid;
 
     /**
      * Constructor.
diff --git a/mod/forum/classes/output/forum_post.php b/mod/forum/classes/output/forum_post.php
index d9866cd59aa..b3862879934 100644
--- a/mod/forum/classes/output/forum_post.php
+++ b/mod/forum/classes/output/forum_post.php
@@ -107,6 +107,9 @@ class forum_post implements \renderable, \templatable {
         'viewfullnames'    => true,
     );
 
+    /** @var \stdClass user record. */
+    protected $userfrom;
+
     /**
      * Builds a renderable forum post
      *
diff --git a/mod/forum/classes/task/cron_task.php b/mod/forum/classes/task/cron_task.php
index ade297fd42f..081da8f2b33 100644
--- a/mod/forum/classes/task/cron_task.php
+++ b/mod/forum/classes/task/cron_task.php
@@ -221,7 +221,7 @@ class cron_task extends \core\task\scheduled_task {
         global $DB;
 
         if (empty($discussionids)) {
-            $this->discussion = [];
+            $this->discussions = [];
         } else {
 
             $requiredfields = [
diff --git a/mod/forum/classes/task/send_user_notifications.php b/mod/forum/classes/task/send_user_notifications.php
index ef7ac0fb90a..042b9bc330d 100644
--- a/mod/forum/classes/task/send_user_notifications.php
+++ b/mod/forum/classes/task/send_user_notifications.php
@@ -93,6 +93,11 @@ class send_user_notifications extends \core\task\adhoc_task {
      */
     protected $inboundmanager;
 
+    /**
+     * @var array List of users.
+     */
+    protected $users = [];
+
     /**
      * Send out messages.
      * @throws \moodle_exception
diff --git a/mod/forum/locallib.php b/mod/forum/locallib.php
index d13042dc31a..205236830a6 100644
--- a/mod/forum/locallib.php
+++ b/mod/forum/locallib.php
@@ -45,6 +45,9 @@ class forum_portfolio_caller extends portfolio_module_caller_base {
     private $posts;
     private $keyedfiles; // just using multifiles isn't enough if we're exporting a full thread
 
+    /** @var context_module context instance. */
+    private $modcontext;
+
     /**
      * @return array
      */
diff --git a/mod/forum/tests/exporters_discussion_test.php b/mod/forum/tests/exporters_discussion_test.php
index 6a2d294260e..68715c79c13 100644
--- a/mod/forum/tests/exporters_discussion_test.php
+++ b/mod/forum/tests/exporters_discussion_test.php
@@ -27,6 +27,10 @@ use mod_forum\local\exporters\discussion as discussion_exporter;
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class exporters_discussion_test extends \advanced_testcase {
+
+    /** @var \mod_forum\local\builders\exported_posts */
+    private $builder;
+
     /**
      * Test set up function.
      */
diff --git a/mod/forum/tests/mail_test.php b/mod/forum/tests/mail_test.php
index 0a4db889641..d1bfe8af0c3 100644
--- a/mod/forum/tests/mail_test.php
+++ b/mod/forum/tests/mail_test.php
@@ -52,6 +52,9 @@ class mail_test extends \advanced_testcase {
      */
     protected $mailsink;
 
+    /** @var \phpunit_event_sink */
+    protected $eventsink;
+
     public function setUp(): void {
         global $CFG;
 
diff --git a/mod/forum/tests/maildigest_test.php b/mod/forum/tests/maildigest_test.php
index 139c9a0b96f..27e026feeac 100644
--- a/mod/forum/tests/maildigest_test.php
+++ b/mod/forum/tests/maildigest_test.php
@@ -41,6 +41,12 @@ class maildigest_test extends \advanced_testcase {
     // Make use of the test generator trait.
     use mod_forum_tests_generator_trait;
 
+    /** @var \phpunit_message_sink */
+    protected $messagesink;
+
+    /** @var \phpunit_message_sink */
+    protected $mailsink;
+
     /**
      * Set up message and mail sinks, and set up other requirements for the
      * cron to be tested here.