diff --git a/lib/classes/output/progress_trace.php b/lib/classes/output/progress_trace.php
index 8259ddb7d71..fdd5d5ecac1 100644
--- a/lib/classes/output/progress_trace.php
+++ b/lib/classes/output/progress_trace.php
@@ -29,9 +29,12 @@ abstract class progress_trace {
      * Output an progress message in whatever format.
      *
      * @param string $message the message to output.
-     * @param integer $depth indent depth for this message.
+     * @param int $depth indent depth for this message.
      */
-    abstract public function output($message, $depth = 0);
+    abstract public function output(
+        string $message,
+        int $depth = 0,
+    );
 
     /**
      * Called when the processing is finished.
diff --git a/lib/classes/output/progress_trace/combined_progress_trace.php b/lib/classes/output/progress_trace/combined_progress_trace.php
index 084114de521..88b34839f48 100644
--- a/lib/classes/output/progress_trace/combined_progress_trace.php
+++ b/lib/classes/output/progress_trace/combined_progress_trace.php
@@ -22,38 +22,29 @@
  * @package core
  */
 class combined_progress_trace extends progress_trace {
-
-    /**
-     * An array of traces.
-     * @var array
-     */
-    protected $traces;
-
     /**
      * Constructs a new instance.
      *
      * @param array $traces multiple traces
      */
-    public function __construct(array $traces) {
-        $this->traces = $traces;
+    public function __construct(
+        /** @var array The list of traces */
+        protected array $traces,
+    ) {
     }
 
-    /**
-     * Output an progress message in whatever format.
-     *
-     * @param string $message the message to output.
-     * @param integer $depth indent depth for this message.
-     */
-    public function output($message, $depth = 0) {
+    #[\Override]
+    public function output(
+        string $message,
+        int $depth = 0,
+    ): void {
         foreach ($this->traces as $trace) {
             $trace->output($message, $depth);
         }
     }
 
-    /**
-     * Called when the processing is finished.
-     */
-    public function finished() {
+    #[\Override]
+    public function finished(): void {
         foreach ($this->traces as $trace) {
             $trace->finished();
         }
diff --git a/lib/classes/output/progress_trace/error_log_progress_trace.php b/lib/classes/output/progress_trace/error_log_progress_trace.php
index f27d5e791a1..2715864bc4d 100644
--- a/lib/classes/output/progress_trace/error_log_progress_trace.php
+++ b/lib/classes/output/progress_trace/error_log_progress_trace.php
@@ -22,25 +22,22 @@
  * @package core
  */
 class error_log_progress_trace extends progress_trace {
-    /** @var string log prefix */
-    protected $prefix;
-
     /**
      * Constructor.
      * @param string $prefix optional log prefix
      */
-    public function __construct($prefix = '') {
-        $this->prefix = $prefix;
+    public function __construct(
+        /** @var string The prefix to use in the error_log messages */
+        protected string $prefix = '',
+    ) {
     }
 
-    /**
-     * Output the trace message.
-     *
-     * @param string $message
-     * @param int $depth
-     * @return void Output is sent to error log.
-     */
-    public function output($message, $depth = 0) {
+    #[\Override]
+    public function output(
+        string $message,
+        int $depth = 0,
+    ): void {
+        // phpcs:ignore moodle.PHP.ForbiddenFunctions.FoundWithAlternative
         error_log($this->prefix . str_repeat('  ', $depth) . $message);
     }
 }
diff --git a/lib/classes/output/progress_trace/html_list_progress_trace.php b/lib/classes/output/progress_trace/html_list_progress_trace.php
index ef1629fb04b..b110ea22ae0 100644
--- a/lib/classes/output/progress_trace/html_list_progress_trace.php
+++ b/lib/classes/output/progress_trace/html_list_progress_trace.php
@@ -22,17 +22,14 @@
  * @package core
  */
 class html_list_progress_trace extends progress_trace {
-    /** @var int */
-    protected $currentdepth = -1;
+    /** @var int The current depth of the trace*/
+    protected int $currentdepth = -1;
 
-    /**
-     * Echo out the list
-     *
-     * @param string $message The message to display
-     * @param int $depth
-     * @return void Output is echoed
-     */
-    public function output($message, $depth = 0) {
+    #[\Override]
+    public function output(
+        string $message,
+        int $depth = 0,
+    ): void {
         $samedepth = true;
         while ($this->currentdepth > $depth) {
             echo "</li>\n</ul>\n";
@@ -54,10 +51,8 @@ class html_list_progress_trace extends progress_trace {
         flush();
     }
 
-    /**
-     * Called when the processing is finished.
-     */
-    public function finished() {
+    #[\Override]
+    public function finished(): void {
         while ($this->currentdepth >= 0) {
             echo "</li>\n</ul>\n";
             $this->currentdepth -= 1;
diff --git a/lib/classes/output/progress_trace/html_progress_trace.php b/lib/classes/output/progress_trace/html_progress_trace.php
index 93208f62c78..d2772e0a09c 100644
--- a/lib/classes/output/progress_trace/html_progress_trace.php
+++ b/lib/classes/output/progress_trace/html_progress_trace.php
@@ -22,14 +22,11 @@
  * @package core
  */
 class html_progress_trace extends progress_trace {
-    /**
-     * Output the trace message.
-     *
-     * @param string $message
-     * @param int $depth
-     * @return void Output is echo'd
-     */
-    public function output($message, $depth = 0) {
+    #[\Override]
+    public function output(
+        string $message,
+        int $depth = 0,
+    ): void {
         echo '<p>', str_repeat('&#160;&#160;', $depth), htmlspecialchars($message, ENT_COMPAT), "</p>\n";
         flush();
     }
diff --git a/lib/classes/output/progress_trace/null_progress_trace.php b/lib/classes/output/progress_trace/null_progress_trace.php
index c0b1def2680..4579b5837cb 100644
--- a/lib/classes/output/progress_trace/null_progress_trace.php
+++ b/lib/classes/output/progress_trace/null_progress_trace.php
@@ -22,13 +22,10 @@
  * @package core
  */
 class null_progress_trace extends progress_trace {
-    /**
-     * Does Nothing
-     *
-     * @param string $message
-     * @param int $depth
-     * @return void Does Nothing
-     */
-    public function output($message, $depth = 0) {
+    #[\Override]
+    public function output(
+        string $message,
+        int $depth = 0,
+    ): void {
     }
 }
diff --git a/lib/classes/output/progress_trace/progress_trace_buffer.php b/lib/classes/output/progress_trace/progress_trace_buffer.php
index 68788c46721..4bf56c1c7e9 100644
--- a/lib/classes/output/progress_trace/progress_trace_buffer.php
+++ b/lib/classes/output/progress_trace/progress_trace_buffer.php
@@ -22,12 +22,8 @@
  * @package core
  */
 class progress_trace_buffer extends progress_trace {
-    /** @var progress_trace */
-    protected $trace;
-    /** @var bool do we pass output out */
-    protected $passthrough;
     /** @var string output buffer */
-    protected $buffer;
+    protected string $buffer = '';
 
     /**
      * Constructor.
@@ -35,20 +31,20 @@ class progress_trace_buffer extends progress_trace {
      * @param progress_trace $trace
      * @param bool $passthrough true means output and buffer, false means just buffer and no output
      */
-    public function __construct(progress_trace $trace, $passthrough = true) {
-        $this->trace       = $trace;
-        $this->passthrough = $passthrough;
+    public function __construct(
+        /** @var progress_trace The progress_trace to pass content to */
+        protected progress_trace $trace,
+        /** @var bool Whether we pass output out */
+        protected bool $passthrough = true,
+    ) {
         $this->buffer      = '';
     }
 
-    /**
-     * Output the trace message.
-     *
-     * @param string $message the message to output.
-     * @param int $depth indent depth for this message.
-     * @return void output stored in buffer
-     */
-    public function output($message, $depth = 0) {
+    #[\Override]
+    public function output(
+        string $message,
+        int $depth = 0,
+    ): void {
         ob_start();
         $this->trace->output($message, $depth);
         $this->buffer .= ob_get_contents();
@@ -59,10 +55,8 @@ class progress_trace_buffer extends progress_trace {
         }
     }
 
-    /**
-     * Called when the processing is finished.
-     */
-    public function finished() {
+    #[\Override]
+    public function finished(): void {
         ob_start();
         $this->trace->finished();
         $this->buffer .= ob_get_contents();
@@ -74,17 +68,18 @@ class progress_trace_buffer extends progress_trace {
     }
 
     /**
-     * Reset internal text buffer.
+     * Reset the internal text buffer.
      */
-    public function reset_buffer() {
+    public function reset_buffer(): void {
         $this->buffer = '';
     }
 
     /**
-     * Return internal text buffer.
+     * Return the internal text buffer.
+     *
      * @return string buffered plain text
      */
-    public function get_buffer() {
+    public function get_buffer(): string {
         return $this->buffer;
     }
 }
diff --git a/lib/classes/output/progress_trace/text_progress_trace.php b/lib/classes/output/progress_trace/text_progress_trace.php
index 21ee17f449b..b9ed47c3962 100644
--- a/lib/classes/output/progress_trace/text_progress_trace.php
+++ b/lib/classes/output/progress_trace/text_progress_trace.php
@@ -22,14 +22,11 @@
  * @package core
  */
 class text_progress_trace extends progress_trace {
-    /**
-     * Output the trace message.
-     *
-     * @param string $message
-     * @param int $depth
-     * @return void Output is echo'd
-     */
-    public function output($message, $depth = 0) {
+    #[\Override]
+    public function output(
+        string $message,
+        int $depth = 0,
+    ): void {
         mtrace(str_repeat('  ', $depth) . $message);
     }
 }