diff --git a/htdocs/Frameworks/art/functions.user.php b/htdocs/Frameworks/art/functions.user.php
index 31aa48908..09165a120 100644
--- a/htdocs/Frameworks/art/functions.user.php
+++ b/htdocs/Frameworks/art/functions.user.php
@@ -18,6 +18,7 @@
      * @param bool $asString
      *
      * @return mixed
+     * @deprecated
      */
     function mod_getIP($asString = false)
     {
@@ -32,6 +33,7 @@ function mod_getIP($asString = false)
      * @param bool $linked
      *
      * @return array
+     * @deprecated
      */
     function &mod_getUnameFromIds($uid, $usereal = false, $linked = false)
     {
@@ -47,6 +49,7 @@ function &mod_getUnameFromIds($uid, $usereal = false, $linked = false)
      * @param bool $linked
      *
      * @return string
+     * @deprecated
      */
     function mod_getUnameFromId($uid, $usereal = 0, $linked = false)
     {
diff --git a/htdocs/class/database/database.php b/htdocs/class/database/database.php
index c980d016f..fcceff4ab 100644
--- a/htdocs/class/database/database.php
+++ b/htdocs/class/database/database.php
@@ -152,6 +152,7 @@ abstract public function exec(string $sql);
 
     /**
      * Legacy alias for writes; kept for BC.
+     * @deprecated
      */
     public function queryF(string $sql)
     {
diff --git a/htdocs/class/errorhandler.php b/htdocs/class/errorhandler.php
index e9fedecc2..5ffd6200a 100644
--- a/htdocs/class/errorhandler.php
+++ b/htdocs/class/errorhandler.php
@@ -34,6 +34,7 @@
  * @author              Kazumi Ono <onokazu@xoops.org>
  * @author              John Neill <catzwolf@xoops.org>
  * @copyright       (c) 2000-2025 XOOPS Project (https://xoops.org)
+ * @deprecated
  */
 class XoopsErrorHandler extends XoopsLogger
 {
diff --git a/htdocs/class/model/read.php b/htdocs/class/model/read.php
index 58d44733e..e27ec469b 100644
--- a/htdocs/class/model/read.php
+++ b/htdocs/class/model/read.php
@@ -198,6 +198,7 @@ public function &getIds(?CriteriaElement $criteria = null)
      * @param  array           $fields   variables to fetch
      * @param  bool            $asObject flag indicating as object, otherwise as array
      * @return array           of objects    {@link XoopsObject}
+     * @deprecated
      */
     public function &getByLimit($limit = 0, $start = 0, ?CriteriaElement $criteria = null, $fields = null, $asObject = true)
     {
@@ -222,6 +223,7 @@ public function &getByLimit($limit = 0, $start = 0, ?CriteriaElement $criteria =
      * @param  bool   $id_as_key - should NOT be used with joint keys
      * @param  bool   $as_object
      * @return array
+     * @deprecated
      */
     public function convertResultSet($result, $id_as_key = false, $as_object = true)
     {
diff --git a/htdocs/class/module.errorhandler.php b/htdocs/class/module.errorhandler.php
index 9ec219ca1..dd22066c3 100644
--- a/htdocs/class/module.errorhandler.php
+++ b/htdocs/class/module.errorhandler.php
@@ -27,6 +27,7 @@
  * @package    kernel
  * @subpackage core
  * @author     Goghs (http://www.eqiao.com/)
+ * @deprecated
  */
 class ErrorHandler
 {
diff --git a/htdocs/class/module.textsanitizer.php b/htdocs/class/module.textsanitizer.php
index 5652533cc..57bef486c 100644
--- a/htdocs/class/module.textsanitizer.php
+++ b/htdocs/class/module.textsanitizer.php
@@ -843,6 +843,7 @@ public function nl2Br($text)
      *
      * @param  string $text
      * @return string
+     * @deprecated
      */
     public function addSlashes($text)
     {
diff --git a/htdocs/class/template.php b/htdocs/class/template.php
index ea6cd4ee3..3babba83d 100644
--- a/htdocs/class/template.php
+++ b/htdocs/class/template.php
@@ -298,6 +298,7 @@ public function xoops_setCacheTime($num = 0)
      *
      * @param string $tpl_var the template variable name
      * @param mixed  &$value  the referenced value to assign
+     * @deprecated
      */
     public function assign_by_ref($tpl_var, &$value)
     {
@@ -311,6 +312,7 @@ public function assign_by_ref($tpl_var, &$value)
      * @param string  $tpl_var the template variable name
      * @param mixed   &$value  the referenced value to append
      * @param boolean $merge   flag if array elements shall be merged
+     * @deprecated
      */
     public function append_by_ref($tpl_var, &$value, $merge = false)
     {
@@ -322,6 +324,7 @@ public function append_by_ref($tpl_var, &$value, $merge = false)
      * deprecated clear_assign
      *
      * @param string $tpl_var the template variable to clear
+     * @deprecated
      */
     public function clear_assign($tpl_var)
     {
@@ -338,6 +341,7 @@ public function clear_assign($tpl_var)
      * @param mixed  $cache_attrs
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function register_function($function, $function_impl, $cacheable = true, $cache_attrs = null)
     {
@@ -349,6 +353,7 @@ public function register_function($function, $function_impl, $cacheable = true,
      * deprecated unregister_function
      *
      * @param string $function name of template function
+     * @deprecated
      */
     public function unregister_function($function)
     {
@@ -367,6 +372,7 @@ public function unregister_function($function)
      *
      * @throws   SmartyException
      * @internal param array $block_functs list of methods that are block format
+     * @deprecated
      */
     public function register_object(
         $object,
@@ -385,6 +391,7 @@ public function register_object(
      * deprecated unregister_object
      *
      * @param string $object name of template object
+     * @deprecated
      */
     public function unregister_object($object)
     {
@@ -401,6 +408,7 @@ public function unregister_object($object)
      * @param mixed  $cache_attrs
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function register_block($block, $block_impl, $cacheable = true, $cache_attrs = null)
     {
@@ -412,6 +420,7 @@ public function register_block($block, $block_impl, $cacheable = true, $cache_at
      * deprecated unregister_block
      *
      * @param string $block name of template function
+     * @deprecated
      */
     public function unregister_block($block)
     {
@@ -427,6 +436,7 @@ public function unregister_block($block)
      * @param bool   $cacheable
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function register_compiler_function($function, $function_impl, $cacheable = true)
     {
@@ -438,6 +448,7 @@ public function register_compiler_function($function, $function_impl, $cacheable
      * deprecated unregister_compiler_function
      *
      * @param string $function name of template function
+     * @deprecated
      */
     public function unregister_compiler_function($function)
     {
@@ -452,6 +463,7 @@ public function unregister_compiler_function($function)
      * @param string $modifier_impl name of PHP function to register
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function register_modifier($modifier, $modifier_impl)
     {
@@ -463,6 +475,7 @@ public function register_modifier($modifier, $modifier_impl)
      * deprecated unregister_modifier
      *
      * @param string $modifier name of template modifier
+     * @deprecated
      */
     public function unregister_modifier($modifier)
     {
@@ -475,6 +488,7 @@ public function unregister_modifier($modifier)
      *
      * @param string $type      name of resource
      * @param array  $functions array of functions to handle resource
+     * @deprecated
      */
     public function register_resource($type, $functions)
     {
@@ -486,6 +500,7 @@ public function register_resource($type, $functions)
      * deprecated unregister_resource
      *
      * @param string $type name of resource
+     * @deprecated
      */
     public function unregister_resource($type)
     {
@@ -499,6 +514,7 @@ public function unregister_resource($type)
      * @param callable $function
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function register_prefilter($function)
     {
@@ -510,6 +526,7 @@ public function register_prefilter($function)
      * deprecated unregister_prefilter
      *
      * @param callable $function
+     * @deprecated
      */
     public function unregister_prefilter($function)
     {
@@ -523,6 +540,7 @@ public function unregister_prefilter($function)
      * @param callable $function
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function register_postfilter($function)
     {
@@ -534,6 +552,7 @@ public function register_postfilter($function)
      * deprecated unregister_postfilter
      *
      * @param callable $function
+     * @deprecated
      */
     public function unregister_postfilter($function)
     {
@@ -547,6 +566,7 @@ public function unregister_postfilter($function)
      * @param callable $function
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function register_outputfilter($function)
     {
@@ -558,6 +578,7 @@ public function register_outputfilter($function)
      * deprecated unregister_outputfilter
      *
      * @param callable $function
+     * @deprecated
      */
     public function unregister_outputfilter($function)
     {
@@ -572,6 +593,7 @@ public function unregister_outputfilter($function)
      * @param string $name filter name
      *
      * @throws \SmartyException
+     * @deprecated
      */
     public function load_filter($type, $name)
     {
@@ -588,6 +610,7 @@ public function load_filter($type, $name)
      * @param string $exp_time   expiration time
      *
      * @return boolean
+     * @deprecated
      */
     public function clear_cache($tpl_file = null, $cache_id = null, $compile_id = null, $exp_time = null)
     {
@@ -601,6 +624,7 @@ public function clear_cache($tpl_file = null, $cache_id = null, $compile_id = nu
      * @param string $exp_time expire time
      *
      * @return boolean
+     * @deprecated
      */
     public function clear_all_cache($exp_time = null)
     {
@@ -618,6 +642,7 @@ public function clear_all_cache($exp_time = null)
      * @return bool
      * @throws \Exception
      * @throws \SmartyException
+     * @deprecated
      */
     public function is_cached($tpl_file, $cache_id = null, $compile_id = null)
     {
@@ -627,6 +652,7 @@ public function is_cached($tpl_file, $cache_id = null, $compile_id = null)
 
     /**
      * deprecated clear_all_assign
+     * @deprecated
      */
     public function clear_all_assign()
     {
@@ -642,6 +668,7 @@ public function clear_all_assign()
      * @param string $exp_time
      *
      * @return boolean results of {@link smarty_core_rm_auto()}
+     * @deprecated
      */
     public function clear_compiled_tpl($tpl_file = null, $compile_id = null, $exp_time = null)
     {
@@ -656,6 +683,7 @@ public function clear_compiled_tpl($tpl_file = null, $compile_id = null, $exp_ti
      *
      * @return bool
      * @throws \SmartyException
+     * @deprecated
      */
     public function template_exists($tpl_file)
     {
@@ -669,6 +697,7 @@ public function template_exists($tpl_file)
      * @param string $name
      *
      * @return array
+     * @deprecated
      */
     public function get_template_vars($name = null)
     {
@@ -682,6 +711,7 @@ public function get_template_vars($name = null)
      * @param string $name
      *
      * @return array
+     * @deprecated
      */
     public function get_config_vars($name = null)
     {
@@ -695,6 +725,7 @@ public function get_config_vars($name = null)
      * @param string $file
      * @param string $section
      * @param string $scope
+     * @deprecated
      */
     public function config_load($file, $section = null, $scope = 'global')
     {
@@ -708,6 +739,7 @@ public function config_load($file, $section = null, $scope = 'global')
      * @param string $name
      *
      * @return object
+     * @deprecated
      */
     public function get_registered_object($name)
     {
@@ -719,6 +751,7 @@ public function get_registered_object($name)
      * deprecated clear_config
      *
      * @param string $var
+     * @deprecated
      */
     public function clear_config($var = null)
     {
diff --git a/htdocs/class/xoopscomments.php b/htdocs/class/xoopscomments.php
index 7948dffbe..5919eaff5 100644
--- a/htdocs/class/xoopscomments.php
+++ b/htdocs/class/xoopscomments.php
@@ -33,6 +33,7 @@
  * @package             kernel
  * @subpackage          comments
  * @access              public
+ * @deprecated since 2.5.4 Use \XoopsComment in /kernel/comment.php instead.
  */
 class XoopsComments extends XoopsObject
 {
diff --git a/htdocs/class/xoopseditor/xoopseditor.php b/htdocs/class/xoopseditor/xoopseditor.php
index cc134cd76..4af15887d 100644
--- a/htdocs/class/xoopseditor/xoopseditor.php
+++ b/htdocs/class/xoopseditor/xoopseditor.php
@@ -206,7 +206,8 @@ public function getList($noHtml = false)
      * XoopsEditorHandler::render()
      *
      * @param mixed $editor
-     * @return
+     * @return string
+     * @deprecated
      */
     public function render($editor)
     {
diff --git a/htdocs/class/xoopstopic.php b/htdocs/class/xoopstopic.php
index 7cf8359b2..a99d8924d 100644
--- a/htdocs/class/xoopstopic.php
+++ b/htdocs/class/xoopstopic.php
@@ -25,6 +25,7 @@
 
 /**
  * Class XoopsTopic
+ * @deprecated
  */
 class XoopsTopic
 {
diff --git a/htdocs/include/cp_functions.php b/htdocs/include/cp_functions.php
index b80eca59d..acc916406 100644
--- a/htdocs/include/cp_functions.php
+++ b/htdocs/include/cp_functions.php
@@ -190,6 +190,7 @@ function xoops_module_get_admin_menu()
  *
  * @param string $content
  * @return bool
+ * @deprecated since version 2.5.0 This function is deprecated and should not be used. No replacement available.
  */
 function xoops_module_write_admin_menu($content)
 {
diff --git a/htdocs/include/functions.legacy.php b/htdocs/include/functions.legacy.php
index 94df01e6e..28829b137 100644
--- a/htdocs/include/functions.legacy.php
+++ b/htdocs/include/functions.legacy.php
@@ -23,6 +23,7 @@
  * @param  string $module
  * @param  string $default
  * @return bool
+ * @deprecated
  */
 
 // Backward compatibility for 2.2*
@@ -37,6 +38,7 @@ function xoops_load_lang_file($name, $module = '', $default = 'english')
  * @param int $docheck
  *
  * @return mixed
+ * @deprecated
  */
 function xoops_refcheck($docheck = 1)
 {
@@ -49,6 +51,7 @@ function xoops_refcheck($docheck = 1)
  * @param $userid
  *
  * @return string
+ * @deprecated
  */
 function xoops_getLinkedUnameFromId($userid)
 {
@@ -58,18 +61,20 @@ function xoops_getLinkedUnameFromId($userid)
     return XoopsUserUtility::getUnameFromId($userid, false, true);
 }
 
-/*
+/**
  * Function to display banners in all pages
- */
+* @deprecated
+*/
 function showbanner()
 {
     $GLOBALS['xoopsLogger']->addDeprecated('Function ' . __FUNCTION__ . '() is deprecated, use xoops_getbanner instead');
     echo xoops_getbanner();
 }
 
-/*
+/**
  * This function is deprecated. Do not use!
- */
+ * @deprecated
+*/
 function getTheme()
 {
     $GLOBALS['xoopsLogger']->addDeprecated('Function ' . __FUNCTION__ . "() is deprecated, use \$xoopsConfig['theme_set'] directly");
@@ -85,6 +90,7 @@ function getTheme()
  * @param string $theme
  *
  * @return string
+ * @deprecated
  */
 function getcss($theme = '')
 {
@@ -95,6 +101,7 @@ function getcss($theme = '')
 
 /**
  * @return XoopsMailer|XoopsMailerLocal
+ * @deprecated
  */
 function getMailer()
 {
@@ -104,9 +111,10 @@ function getMailer()
     return $mailer;
 }
 
-/*
+/**
  * Functions to display dhtml loading image box
- */
+ * @deprecated
+*/
 function OpenWaitBox()
 {
     $GLOBALS['xoopsLogger']->addDeprecated('Function ' . __FUNCTION__ . '() is deprecated');
@@ -152,6 +160,10 @@ function ap_showWaitMessage(div,flag)
     </script>";
 }
 
+/**
+ * @return void
+ * @deprecated
+ */
 function CloseWaitBox()
 {
     $GLOBALS['xoopsLogger']->addDeprecated('Function ' . __FUNCTION__ . '() is deprecated');
diff --git a/htdocs/include/old_theme_functions.php b/htdocs/include/old_theme_functions.php
index b89acb62a..ad5b884ee 100644
--- a/htdocs/include/old_theme_functions.php
+++ b/htdocs/include/old_theme_functions.php
@@ -21,6 +21,7 @@
 if (!function_exists('opentable')) {
     /**
      * @param string $width
+     * @deprecated
      */
     function openTable($width = '100%')
     {
@@ -30,6 +31,10 @@ function openTable($width = '100%')
 }
 
 if (!function_exists('closetable')) {
+    /**
+     * @return void
+     * @deprecated
+     */
     function closeTable()
     {
         $GLOBALS['xoopsLogger']->addDeprecated("Function '" . __FUNCTION__ . "' in '" . __FILE__ . "' is deprecated, should not be used any more");
@@ -41,6 +46,7 @@ function closeTable()
     /**
      * @param $title
      * @param $content
+     * @deprecated
      */
     function themecenterposts($title, $content)
     {
diff --git a/htdocs/kernel/module.php b/htdocs/kernel/module.php
index ff7fca87d..7fa5500f7 100644
--- a/htdocs/kernel/module.php
+++ b/htdocs/kernel/module.php
@@ -521,6 +521,7 @@ public function checkAccess()
      * @param string $type
      *
      * @return bool
+     * @deprecated
      */
     public function loadLanguage($type = 'main')
     {
@@ -531,6 +532,7 @@ public function loadLanguage($type = 'main')
 
     /**
      * @return bool
+     * @deprecated
      */
     public function loadErrorMessages()
     {
@@ -541,6 +543,7 @@ public function loadErrorMessages()
 
     /**
      * @return bool
+     * @deprecated
      */
     public function getCurrentPage()
     {
@@ -554,6 +557,7 @@ public function getCurrentPage()
      * @param array $accessgroups
      *
      * @return bool
+     * @deprecated
      */
     public function install($admingroups = [], $accessgroups = [])
     {
@@ -564,6 +568,7 @@ public function install($admingroups = [], $accessgroups = [])
 
     /**
      * @return bool
+     * @deprecated
      */
     public function update()
     {
@@ -574,6 +579,7 @@ public function update()
 
     /**
      * @return bool
+     * @deprecated
      */
     public function insert()
     {
@@ -594,6 +600,7 @@ public function executeSQL()
 
     /**
      * @return bool
+     * @deprecated
      */
     public function insertTemplates()
     {
@@ -607,6 +614,7 @@ public function insertTemplates()
      * @param bool $block
      *
      * @return bool
+     * @deprecated
      */
     public function gettemplate($template, $block = false)
     {
@@ -617,6 +625,7 @@ public function gettemplate($template, $block = false)
 
     /**
      * @return bool
+     * @deprecated
      */
     public function insertBlocks()
     {
@@ -627,6 +636,7 @@ public function insertBlocks()
 
     /**
      * @return bool
+     * @deprecated
      */
     public function insertConfigCategories()
     {
@@ -637,6 +647,7 @@ public function insertConfigCategories()
 
     /**
      * @return bool
+     * @deprecated
      */
     public function insertConfig()
     {
@@ -647,6 +658,7 @@ public function insertConfig()
 
     /**
      * @return bool
+     * @deprecated
      */
     public function insertProfileFields()
     {
@@ -660,6 +672,7 @@ public function insertProfileFields()
      * @param int $state
      *
      * @return bool
+     * @deprecated
      */
     public function executeScript($type, $state = 2)
     {
@@ -673,6 +686,7 @@ public function executeScript($type, $state = 2)
      * @param $type
      *
      * @return bool
+     * @deprecated
      */
     public function insertGroupPermissions($groups, $type)
     {
diff --git a/htdocs/register.php b/htdocs/register.php
index bf18d6dce..43f936bb0 100644
--- a/htdocs/register.php
+++ b/htdocs/register.php
@@ -49,6 +49,7 @@
  * @param $vpass
  *
  * @return bool|string
+ * @deprecated
  */
 function userCheck($uname, $email, $pass, $vpass)
 {