diff --git a/public/lib/classes/exception/xml_format_exception.php b/public/lib/classes/exception/xml_format_exception.php
index e1393edc814..edaafa639b4 100644
--- a/public/lib/classes/exception/xml_format_exception.php
+++ b/public/lib/classes/exception/xml_format_exception.php
@@ -26,24 +26,23 @@ use stdClass;
  * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class xml_format_exception extends moodle_exception {
-
-    /** @var string */
-    public $errorstring;
-    /** @var string */
-    public $char;
     /**
      * Constructor function
      *
-     * @param string $errorstring Errorstring
-     * @param int $line Linenumber
-     * @param string $char Errorcharacter
+     * @param string|null $errorstring Error string
+     * @param int $line Line number
+     * @param int $char Character number
      * @param string $link Link
      */
-    public function __construct($errorstring, $line, $char, $link = '') {
-        $this->errorstring = $errorstring;
-        $this->line = $line;
-        $this->char = $char;
-
+    public function __construct(
+        /** @var ?string Error string */
+        public ?string $errorstring,
+        /** @var int Line number */
+        public int $line,
+        /** @var int Character number */
+        public int $char,
+        string $link = '',
+    ) {
         $a = new stdClass();
         $a->errorstring = $errorstring;
         $a->errorline = $line;
diff --git a/public/lib/classes/xml_parser.php b/public/lib/classes/xml_parser.php
index 3a1af390ff3..765b19522eb 100644
--- a/public/lib/classes/xml_parser.php
+++ b/public/lib/classes/xml_parser.php
@@ -17,6 +17,7 @@
 namespace core;
 
 use core\exception\xml_format_exception;
+use XMLParser;
 
 /**
  * Class for parsing xml files.
@@ -35,40 +36,44 @@ use core\exception\xml_format_exception;
  */
 class xml_parser {
     /** @var array resulting $xml tree */
-    private $xml;
+    private array $xml;
     /** @var array stores references to constructed $xml tree */
-    private $current;
+    private array $current;
     /** @var int tores the level in the XML tree */
-    private $level;
+    private int $level;
+
     /**
      * Is called when tags are opened.
      *
      * Note: Used by xml element handler as callback.
      *
-     * @author Kilian Singer
-     * @param resource $parser The XML parser resource.
+     * @param XMLParser $parser The XML parser resource.
      * @param string $name The XML source to parse.
      * @param array $attrs Stores attributes of XML tag.
      */
-    private function startelement($parser, $name, $attrs) {
+    private function startelement(
+        XMLParser $parser,
+        string $name,
+        array $attrs,
+    ): void {
         $current = &$this->current;
         $level = &$this->level;
         if (!empty($name)) {
             if ($level == 0) {
-                $current[$level][$name] = array();
+                $current[$level][$name] = [];
                 $current[$level][$name]["@"] = $attrs; // Attribute.
-                $current[$level][$name]["#"] = array(); // Other tags.
+                $current[$level][$name]["#"] = []; // Other tags.
                 $current[$level + 1] = & $current[$level][$name]["#"];
                 $level++;
             } else {
                 if (empty($current[$level][$name])) {
-                    $current[$level][$name] = array();
+                    $current[$level][$name] = [];
                 }
                 $siz = count($current[$level][$name]);
                 if (!empty($attrs)) {
                     $current[$level][$name][$siz]["@"] = $attrs; // Attribute.
                 }
-                $current[$level][$name][$siz]["#"] = array(); // Other tags.
+                $current[$level][$name][$siz]["#"] = []; // Other tags.
                 $current[$level + 1] = & $current[$level][$name][$siz]["#"];
                 $level++;
             }
@@ -80,11 +85,13 @@ class xml_parser {
      *
      * Note: Used by xml element handler as callback.
      *
-     * @author Kilian Singer
-     * @param resource $parser The XML parser resource.
+     * @param XMLParser $parser The XML parser resource.
      * @param string $name The XML source to parse.
      */
-    private function endelement($parser, $name) {
+    private function endelement(
+        XMLParser $parser,
+        string $name,
+    ): void {
         $current = &$this->current;
         $level = &$this->level;
         if (!empty($name)) {
@@ -104,11 +111,13 @@ class xml_parser {
      *
      * Note: Used by xml element handler as callback.
      *
-     * @author Kilian Singer
-     * @param resource $parser The XML parser resource.
+     * @param XMLParser $parser The XML parser resource.
      * @param string $data The XML source to parse.
      */
-    private function characterdata($parser, $data) {
+    private function characterdata(
+        XMLParser $parser,
+        string $data,
+    ): void {
         $current = &$this->current;
         $level = &$this->level;
         if (($data == "0") || (!empty($data) && trim($data) != "")) {
@@ -136,18 +145,23 @@ class xml_parser {
      *
      * Note: Interface is kept equal to previous version.
      *
-     * @author Kilian Singer
      * @param string $data the XML source to parse.
      * @param int $whitespace If set to 1 allows the parser to skip "space" characters in xml document. Default is 1
      * @param string $encoding Specify an OUTPUT encoding. If not specified, it defaults to UTF-8.
-     * @param bool $reporterrors if set to true, then a {@link xml_format_exception}
+     * @param bool $reporterrors if set to true, then a {@see xml_format_exception}
      *      exception will be thrown if the XML is not well-formed. Otherwise errors are ignored.
      * @return array|false representation of the parsed XML.
+     * @throws xml_format_exception
      */
-    public function parse($data, $whitespace = 1, $encoding = 'UTF-8', $reporterrors = false) {
+    public function parse(
+        string $data,
+        int $whitespace = 1,
+        string $encoding = 'UTF-8',
+        bool $reporterrors = false,
+    ): array|false {
         $data = trim($data);
-        $this->xml = array();
-        $this->current = array();
+        $this->xml = [];
+        $this->current = [];
         $this->level = 0;
         $this->current[0] = & $this->xml;
         $parser = xml_parser_create($encoding);
@@ -164,9 +178,11 @@ class xml_parser {
         if ($reporterrors) {
             $errorcode = xml_get_error_code($parser);
             if ($errorcode) {
-                $exception = new xml_format_exception(xml_error_string($errorcode),
+                $exception = new xml_format_exception(
+                    xml_error_string($errorcode),
                     xml_get_current_line_number($parser),
-                    xml_get_current_column_number($parser));
+                    xml_get_current_column_number($parser),
+                );
                 xml_parser_free($parser);
                 throw $exception;
             }