diff --git a/mod/quiz/lib.php b/mod/quiz/lib.php
index efab18bca40..020f0346a86 100644
--- a/mod/quiz/lib.php
+++ b/mod/quiz/lib.php
@@ -120,6 +120,7 @@ function quiz_add_instance($quiz) {
  * will update an existing instance with new data.
  *
  * @param stdClass $quiz the data that came from the form.
+ * @param stdClass $mform no longer used.
  * @return mixed true on success, false or a string error message on failure.
  */
 function quiz_update_instance($quiz, $mform) {
@@ -1251,9 +1252,8 @@ function quiz_after_add_or_update($quiz) {
  * If $override is non-zero, then it updates only the events
  * associated with the specified override.
  *
- * @uses QUIZ_MAX_EVENT_LENGTH
  * @param stdClass $quiz the quiz object.
- * @param stdClass optional $override limit to a specific override
+ * @param stdClass|null $override limit to a specific override
  */
 function quiz_update_events($quiz, $override = null) {
     global $DB;
diff --git a/mod/quiz/locallib.php b/mod/quiz/locallib.php
index b408148cd13..f18deebca6f 100644
--- a/mod/quiz/locallib.php
+++ b/mod/quiz/locallib.php
@@ -79,13 +79,13 @@ define('QUIZ_SHOWIMAGE_LARGE', 2);
  * user starting at the current time. The ->id field is not set. The object is
  * NOT written to the database.
  *
- * @param stdClass $quizobj the quiz object to create an attempt for.
+ * @param quiz_settings $quizobj the quiz object to create an attempt for.
  * @param int $attemptnumber the sequence number for the attempt.
  * @param stdClass|false $lastattempt the previous attempt by this user, if any. Only needed
  *         if $attemptnumber > 1 and $quiz->attemptonlast is true.
  * @param int $timenow the time the attempt was started at.
  * @param bool $ispreview whether this new attempt is a preview.
- * @param int $userid  the id of the user attempting this quiz.
+ * @param int|null $userid  the id of the user attempting this quiz.
  *
  * @return stdClass the newly created attempt object.
  */
@@ -1379,7 +1379,6 @@ function quiz_attempt_state_name($state) {
  * @param stdClass $question the question.
  * @param string $returnurl url to return to after action is done.
  * @param int $variant which question variant to preview (optional).
- * @param bool $random if question is random, true.
  * @return string html for a number of icons linked to action pages for a
  * question - preview and edit / view icons depending on user capabilities.
  */
@@ -1610,6 +1609,7 @@ function quiz_get_combined_reviewoptions($quiz, $attempts) {
 /**
  * Sends a confirmation message to the student confirming that the attempt was processed.
  *
+ * @param stdClass $recipient user object for the recipient.
  * @param stdClass $a lots of useful information that can be used in the message
  *      subject and body.
  * @param bool $studentisonline is the student currently interacting with Moodle?
@@ -1660,6 +1660,7 @@ function quiz_send_confirmation($recipient, $a, $studentisonline) {
  * Sends notification messages to the interested parties that assign the role capability
  *
  * @param stdClass $recipient user object of the intended recipient
+ * @param stdClass $submitter user object for the user who submitted the attempt.
  * @param stdClass $a associative array of replaceable fields for the templates
  *
  * @return int|false as for {@link message_send()}.
diff --git a/mod/quiz/mod_form.php b/mod/quiz/mod_form.php
index 753f5245376..44cff553ebd 100644
--- a/mod/quiz/mod_form.php
+++ b/mod/quiz/mod_form.php
@@ -41,8 +41,11 @@ class mod_quiz_mod_form extends moodleform_mod {
     /** @var array options to be used with date_time_selector fields in the quiz. */
     public static $datefieldoptions = ['optional' => true];
 
+    /** @var array caches the quiz overall feedback, for convenience. */
     protected $_feedbacks;
-    protected static $reviewfields = []; // Initialised in the constructor.
+
+    /** @var array for convenience stores the list of types of review option. Initialised in the constructor. */
+    protected static $reviewfields = [];
 
     /** @var int the max number of attempts allowed in any user or group override on this quiz. */
     protected $maxattemptsanyoverride = null;
@@ -61,7 +64,7 @@ class mod_quiz_mod_form extends moodleform_mod {
     }
 
     protected function definition() {
-        global $COURSE, $CFG, $DB, $PAGE;
+        global $CFG, $DB, $PAGE;
         $quizconfig = get_config('quiz');
         $mform = $this->_form;
 
diff --git a/mod/quiz/report/grading/gradingsettings_form.php b/mod/quiz/report/grading/gradingsettings_form.php
index c2b90de3d6d..49189ac30f7 100644
--- a/mod/quiz/report/grading/gradingsettings_form.php
+++ b/mod/quiz/report/grading/gradingsettings_form.php
@@ -35,9 +35,16 @@ require_once($CFG->libdir . '/formslib.php');
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class quiz_grading_settings_form extends moodleform {
+    /** @var bool whether the user has asked to include automatically graded attempts. */
     protected $includeauto;
+
+    /** @var array extra hidden fields to add to the form. Things like cm id. */
     protected $hidden = [];
+
+    /** @var stdClass data about how many attempts of each type their are. */
     protected $counts;
+
+    /** @var bool Whether the user has permission to see user names. */
     protected $shownames;
 
     /** @var bool $showcustomfields whether custom field values should be shown. */
diff --git a/mod/quiz/report/overview/overview_table.php b/mod/quiz/report/overview/overview_table.php
index 30fedf874a9..5e96f27baf4 100644
--- a/mod/quiz/report/overview/overview_table.php
+++ b/mod/quiz/report/overview/overview_table.php
@@ -25,6 +25,7 @@ use mod_quiz\quiz_attempt;
  */
 class quiz_overview_table extends attempts_report_table {
 
+    /** @var array used to store information about which questoins have been regraded. */
     protected $regradedqs = [];
 
     /**
diff --git a/mod/quiz/report/overview/report.php b/mod/quiz/report/overview/report.php
index 3ae29602f6d..0feea206cce 100644
--- a/mod/quiz/report/overview/report.php
+++ b/mod/quiz/report/overview/report.php
@@ -452,15 +452,16 @@ class quiz_overview_report extends attempts_report {
     /**
      * Regrade attempts for this quiz, exactly which attempts are regraded is
      * controlled by the parameters.
+     *
      * @param stdClass $quiz the quiz settings.
      * @param bool $dryrun if true, do a pretend regrade, otherwise do it for real.
-     * @param \core\dml\sql_join|array $groupstudentsjoins empty for all attempts, otherwise regrade attempts
+     * @param \core\dml\sql_join|null $groupstudentsjoins empty for all attempts, otherwise regrade attempts
      * for these users.
      * @param array $attemptids blank for all attempts, otherwise only regrade
      * attempts whose id is in this list.
      */
     protected function regrade_attempts($quiz, $dryrun = false,
-            \core\dml\sql_join$groupstudentsjoins = null, $attemptids = []) {
+            core\dml\sql_join $groupstudentsjoins = null, $attemptids = []) {
         global $DB;
         $this->unlock_session();
 
@@ -679,11 +680,9 @@ class quiz_overview_report extends attempts_report {
     }
 
     /**
-     * Update the final grades for all attempts. This method is used following
-     * a regrade.
+     * Update the final grades for all attempts. This method is used following a regrade.
+     *
      * @param stdClass $quiz the quiz settings.
-     * @param array $userids only update scores for these userids.
-     * @param array $attemptids attemptids only update scores for these attempt ids.
      */
     protected function update_overall_grades($quiz) {
         quiz_update_all_attempt_sumgrades($quiz);
diff --git a/mod/quiz/report/responses/tests/responses_from_steps_walkthrough_test.php b/mod/quiz/report/responses/tests/responses_from_steps_walkthrough_test.php
index cf8a4589a82..07c06df8cc9 100644
--- a/mod/quiz/report/responses/tests/responses_from_steps_walkthrough_test.php
+++ b/mod/quiz/report/responses/tests/responses_from_steps_walkthrough_test.php
@@ -41,6 +41,9 @@ class responses_from_steps_walkthrough_test extends \mod_quiz\attempt_walkthroug
         return  __DIR__."/fixtures/{$setname}{$test}.csv";
     }
 
+    /**
+     * @var string[] names of the files which contain the test data.
+     */
     protected $files = ['questions', 'steps', 'responses'];
 
     /**
diff --git a/mod/quiz/report/statistics/tests/stats_from_steps_walkthrough_test.php b/mod/quiz/report/statistics/tests/stats_from_steps_walkthrough_test.php
index dda22ba9691..2f95f61674b 100644
--- a/mod/quiz/report/statistics/tests/stats_from_steps_walkthrough_test.php
+++ b/mod/quiz/report/statistics/tests/stats_from_steps_walkthrough_test.php
@@ -57,6 +57,9 @@ class stats_from_steps_walkthrough_test extends \mod_quiz\attempt_walkthrough_fr
         return  __DIR__."/fixtures/{$setname}{$test}.csv";
     }
 
+    /**
+     * @var string[] names of the files which contain the test data.
+     */
     protected $files = ['questions', 'steps', 'results', 'qstats', 'responsecounts'];
 
     /**
diff --git a/mod/quiz/tests/attempt_walkthrough_from_csv_test.php b/mod/quiz/tests/attempt_walkthrough_from_csv_test.php
index c951c028254..86a801d442c 100644
--- a/mod/quiz/tests/attempt_walkthrough_from_csv_test.php
+++ b/mod/quiz/tests/attempt_walkthrough_from_csv_test.php
@@ -35,6 +35,9 @@ require_once($CFG->dirroot . '/mod/quiz/locallib.php');
  */
 class attempt_walkthrough_from_csv_test extends \advanced_testcase {
 
+    /**
+     * @var string[] names of the files which contain the test data.
+     */
     protected $files = ['questions', 'steps', 'results'];
 
     /**
diff --git a/mod/quiz/tests/custom_completion_test.php b/mod/quiz/tests/custom_completion_test.php
index 6b05052dcae..08b87c306c2 100644
--- a/mod/quiz/tests/custom_completion_test.php
+++ b/mod/quiz/tests/custom_completion_test.php
@@ -25,6 +25,7 @@ use grade_item;
 use mod_quiz\completion\custom_completion;
 use question_engine;
 use mod_quiz\quiz_settings;
+use stdClass;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -462,14 +463,15 @@ class custom_completion_test extends advanced_testcase {
     /**
      * Set up moduleinfo object sample data for quiz instance.
      *
-     * @param stdClass $cm course-module instance
+     * @param cm_info $cm course-module instance
      * @param stdClass $quiz quiz instance data.
      * @param stdClass $course Course related data.
      * @param int $gradepass Grade to pass and completed completion.
      * @param string $grademethod grade attempt method.
-     * @return \stdClass
+     * @return stdClass
      */
-    private function prepare_module_info(object $cm, object $quiz, object $course, int $gradepass, string $grademethod): \stdClass {
+    private function prepare_module_info(cm_info $cm, stdClass $quiz, stdClass $course,
+            int $gradepass, string $grademethod): \stdClass {
         $grouping = $this->getDataGenerator()->create_grouping(['courseid' => $course->id]);
         // Module test values.
         $moduleinfo = new \stdClass();