diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5e8f27d3267..4c3ee2342fa 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,7 +35,7 @@ jobs:
       matrix:
         include:
           - {php-version: "8.2"} # Lint on lower PHP version to detected too early usage of new syntaxes
-          - {php-version: "8.3"} # Lint on higher PHP version to detected deprecated elements usage
+          - {php-version: "8.4"} # Lint on higher PHP version to detected deprecated elements usage
     env:
       COMPOSE_FILE: ".github/actions/docker-compose-app.yml"
       APPLICATION_ROOT: "${{ github.workspace }}"
@@ -116,11 +116,11 @@ jobs:
             MATRIX='
               {
                 "include": [
-                  {"php-version": "8.3", "db-image": "mariadb:11.4"},
-                  {"php-version": "8.3", "db-image": "mysql:8.4"},
+                  {"php-version": "8.4", "db-image": "mariadb:11.4"},
+                  {"php-version": "8.4", "db-image": "mysql:8.4"},
                   {"php-version": "8.2", "db-image": "mariadb:11.4"},
-                  {"php-version": "8.3", "db-image": "mariadb:10.5"},
-                  {"php-version": "8.3", "db-image": "percona:8.0"}
+                  {"php-version": "8.4", "db-image": "mariadb:10.5"},
+                  {"php-version": "8.4", "db-image": "percona:8.0"}
                 ]
               }
             '
@@ -128,8 +128,8 @@ jobs:
             MATRIX='
               {
                 "include": [
-                  {"php-version": "8.3", "db-image": "mariadb:11.4"},
-                  {"php-version": "8.3", "db-image": "mysql:8.4"}
+                  {"php-version": "8.4", "db-image": "mariadb:11.4"},
+                  {"php-version": "8.4", "db-image": "mysql:8.4"}
                 ]
               }
             '
diff --git a/composer.json b/composer.json
index 4abf6cdba5c..53d9cc87528 100644
--- a/composer.json
+++ b/composer.json
@@ -104,8 +104,8 @@
     },
     "require-dev": {
         "ext-xml": "*",
-        "atoum/atoum": "^4.2",
-        "atoum/stubs": "^2.6",
+        "atoum/atoum": "dev-main#e43a6a84809635cf5dcdf80bf3c773e7cf1d5a04",
+        "atoum/stubs": "dev-master#fb8890f347a7ecf1e3cf2b5a139a8b038359a6ab",
         "friendsoftwig/twigcs": "^6.4",
         "glpi-project/tools": "^0.7",
         "mikey179/vfsstream": "^1.6",
@@ -188,19 +188,21 @@
         "post-install-cmd": [
             "@php -r \"file_put_contents('.composer.hash', sha1_file('composer.lock'));\"",
             "@php -f vendor/bin/build_hw_jsons",
-            "patch -f -p1 -d vendor/laminas/laminas-mail/ < tools/patches/laminas-mail-invalid-header-ignore.patch || true",
-            "patch -f -p1 -d vendor/laminas/laminas-mail/ < tools/patches/laminas-mail-address-no-length-check.patch || true",
-            "patch -f -p1 -d vendor/guzzlehttp/guzzle/ < tools/patches/guzzle-http-client-restrict-http-methods.patch || true"
+            "@patch"
         ],
         "post-update-cmd": [
             "@php -r \"file_put_contents('.composer.hash', sha1_file('composer.lock'));\"",
             "@php -f vendor/bin/build_hw_jsons",
-            "patch -f -p1 -d vendor/laminas/laminas-mail/ < tools/patches/laminas-mail-invalid-header-ignore.patch || true",
-            "patch -f -p1 -d vendor/laminas/laminas-mail/ < tools/patches/laminas-mail-address-no-length-check.patch || true",
-            "patch -f -p1 -d vendor/guzzlehttp/guzzle/ < tools/patches/guzzle-http-client-restrict-http-methods.patch || true"
+            "@patch"
         ],
         "build": [
             "bin/console dependencies install"
+        ],
+        "patch": [
+            "patch -f -p1 -d vendor/laminas/laminas-mail/ < tools/patches/laminas-mail-invalid-header-ignore.patch || true",
+            "patch -f -p1 -d vendor/laminas/laminas-mail/ < tools/patches/laminas-mail-address-no-length-check.patch || true",
+            "patch -f -p1 -d vendor/guzzlehttp/guzzle/ < tools/patches/guzzle-http-client-restrict-http-methods.patch || true",
+            "patch -f -p1 -d vendor/apereo/phpcas/ < tools/patches/apereo-phpcas-php84.patch || true"
         ]
     }
 }
diff --git a/composer.lock b/composer.lock
index d40b9cab3f1..70515fb32a8 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "f7fbe4971a89637e80066017f3eeef72",
+    "content-hash": "093f173c565f7d2b5be80c807843fc1a",
     "packages": [
         {
             "name": "apereo/phpcas",
@@ -8986,16 +8986,16 @@
     "packages-dev": [
         {
             "name": "atoum/atoum",
-            "version": "4.2.0",
+            "version": "dev-main",
             "source": {
                 "type": "git",
                 "url": "https://github.com/atoum/atoum.git",
-                "reference": "fd9a339de252ea774ab755b3fd25dd19be2dbefb"
+                "reference": "e43a6a84809635cf5dcdf80bf3c773e7cf1d5a04"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/atoum/atoum/zipball/fd9a339de252ea774ab755b3fd25dd19be2dbefb",
-                "reference": "fd9a339de252ea774ab755b3fd25dd19be2dbefb",
+                "url": "https://api.github.com/repos/atoum/atoum/zipball/e43a6a84809635cf5dcdf80bf3c773e7cf1d5a04",
+                "reference": "e43a6a84809635cf5dcdf80bf3c773e7cf1d5a04",
                 "shasum": ""
             },
             "require": {
@@ -9016,6 +9016,7 @@
                 "ext-mbstring": "Provides support for UTF-8 strings",
                 "ext-xdebug": "Provides code coverage report (>= 2.3)"
             },
+            "default-branch": true,
             "bin": [
                 "bin/atoum"
             ],
@@ -9067,27 +9068,28 @@
             ],
             "support": {
                 "issues": "https://github.com/atoum/atoum/issues",
-                "source": "https://github.com/atoum/atoum/tree/4.2.0"
+                "source": "https://github.com/atoum/atoum/tree/main"
             },
-            "time": "2023-07-30T12:52:23+00:00"
+            "time": "2024-07-31T12:02:10+00:00"
         },
         {
             "name": "atoum/stubs",
-            "version": "2.6.0",
+            "version": "dev-master",
             "source": {
                 "type": "git",
                 "url": "https://github.com/atoum/stubs.git",
-                "reference": "df8b73b0358de7283ecba91d8f4a9683f583993d"
+                "reference": "fb8890f347a7ecf1e3cf2b5a139a8b038359a6ab"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/atoum/stubs/zipball/df8b73b0358de7283ecba91d8f4a9683f583993d",
-                "reference": "df8b73b0358de7283ecba91d8f4a9683f583993d",
+                "url": "https://api.github.com/repos/atoum/stubs/zipball/fb8890f347a7ecf1e3cf2b5a139a8b038359a6ab",
+                "reference": "fb8890f347a7ecf1e3cf2b5a139a8b038359a6ab",
                 "shasum": ""
             },
             "suggest": {
                 "atoum/atoum": "Include atoum in your projet dependencies"
             },
+            "default-branch": true,
             "type": "library",
             "extra": {
                 "branch-alias": {
@@ -9120,7 +9122,7 @@
                 "issues": "https://github.com/atoum/stubs/issues",
                 "source": "https://github.com/atoum/stubs/tree/master"
             },
-            "time": "2018-01-29T22:41:37+00:00"
+            "time": "2024-07-30T18:02:37+00:00"
         },
         {
             "name": "friendsoftwig/twigcs",
@@ -11723,7 +11725,10 @@
     ],
     "aliases": [],
     "minimum-stability": "stable",
-    "stability-flags": [],
+    "stability-flags": {
+        "atoum/atoum": 20,
+        "atoum/stubs": 20
+    },
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
diff --git a/phpunit/functional/TicketTest.php b/phpunit/functional/TicketTest.php
index 25a1ac4e76d..6196a7b5c1d 100644
--- a/phpunit/functional/TicketTest.php
+++ b/phpunit/functional/TicketTest.php
@@ -7579,7 +7579,10 @@ public function testDynamicProperties(): void
     {
         $ticket = new \Ticket();
 
+        $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
         $ticket->plugin_xxx_data = 'test';
+        \error_reporting($reporting_level); // restore previous level
+
         $this->hasPhpLogRecordThatContains(
             'Creation of dynamic property Ticket::$plugin_xxx_data is deprecated',
             LogLevel::INFO
diff --git a/phpunit/functional/ToolboxTest.php b/phpunit/functional/ToolboxTest.php
index 7f9225cbb01..4b82fd36da0 100644
--- a/phpunit/functional/ToolboxTest.php
+++ b/phpunit/functional/ToolboxTest.php
@@ -1080,7 +1080,10 @@ public function testIsValidWebUrl(string $url, bool $result)
 
     public function testDeprecated()
     {
+        $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
         \Toolbox::deprecated('Calling this function is deprecated');
+        \error_reporting($reporting_level); // restore previous level
+
         $this->hasPhpLogRecordThatContains(
             'Calling this function is deprecated',
             LogLevel::INFO
@@ -1090,7 +1093,10 @@ public function testDeprecated()
     public function testDeprecatedPast()
     {
         // Test planned deprecation in the past
+        $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
         \Toolbox::deprecated('Calling this function is deprecated', true, '10.0');
+        \error_reporting($reporting_level); // restore previous level
+
         $this->hasPhpLogRecordThatContains(
             'Calling this function is deprecated',
             LogLevel::INFO
@@ -1100,7 +1106,10 @@ public function testDeprecatedPast()
     public function testDeprecatedCurrent()
     {
         // Test planned deprecation in current version
+        $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
         \Toolbox::deprecated('Calling this function is deprecated', true, GLPI_VERSION);
+        \error_reporting($reporting_level); // restore previous level
+
         $this->hasPhpLogRecordThatContains(
             'Calling this function is deprecated',
             LogLevel::INFO
@@ -1110,7 +1119,10 @@ public function testDeprecatedCurrent()
     public function testFutureDeprecated()
     {
         // Test planned deprecation in the future does NOT throw an error
+        $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
         \Toolbox::deprecated('Calling this function is deprecated', true, '99.0');
+        \error_reporting($reporting_level); // restore previous level
+
         $this->assertTrue(true); //non empty test
     }
 
diff --git a/public/index.php b/public/index.php
index e0f2b05cc1a..c5fe79be48a 100755
--- a/public/index.php
+++ b/public/index.php
@@ -37,8 +37,8 @@
 
 // Check PHP version not to have trouble
 // Need to be the very fist step before any include
-if (version_compare(PHP_VERSION, '8.2.0', '<') || version_compare(PHP_VERSION, '8.3.999', '>')) {
-    exit('PHP version must be between 8.2 and 8.3.');
+if (version_compare(PHP_VERSION, '8.2.0', '<') || version_compare(PHP_VERSION, '8.4.999', '>')) {
+    exit('PHP version must be between 8.2 and 8.4.');
 }
 
 // Check the resources state before trying to instanciate the Kernel.
diff --git a/src/Consumable.php b/src/Consumable.php
index 54d83e93e2f..2e04a699499 100644
--- a/src/Consumable.php
+++ b/src/Consumable.php
@@ -197,7 +197,7 @@ public static function getMassiveActionsForItemtype(
         array &$actions,
         $itemtype,
         $is_deleted = 0,
-        CommonDBTM $checkitem = null
+        ?CommonDBTM $checkitem = null
     ) {
         // Special actions only for self
         if ($itemtype !== static::class) {
diff --git a/src/Glpi/Application/ErrorHandler.php b/src/Glpi/Application/ErrorHandler.php
index 0d083588502..9a3914bd6bd 100644
--- a/src/Glpi/Application/ErrorHandler.php
+++ b/src/Glpi/Application/ErrorHandler.php
@@ -63,7 +63,7 @@ class ErrorHandler
         E_USER_ERROR        => LogLevel::ERROR,
         E_USER_WARNING      => LogLevel::WARNING,
         E_USER_NOTICE       => LogLevel::NOTICE,
-        E_STRICT            => LogLevel::NOTICE,
+        2048                => LogLevel::NOTICE, // 2048 = deprecated E_STRICT
         E_RECOVERABLE_ERROR => LogLevel::ERROR,
         E_DEPRECATED        => LogLevel::INFO,
         E_USER_DEPRECATED   => LogLevel::INFO,
@@ -227,9 +227,34 @@ public function register(): void
             set_exception_handler([$this, 'handleException']);
         }
 
-        // Force reporting of all errors, to ensure that all log levels that are supposed to be
-        // pushed in logs according to `GLPI_LOG_LVL`/`GLPI_ENVIRONMENT_TYPE` are actually reported.
-        error_reporting(E_ALL);
+        // Adjust reporting level to the environment, to ensure that all the errors supposed to be logged are
+        // actually reported, and to prevent reporting other errors.
+        $reporting_level = E_ALL;
+        foreach (self::ERROR_LEVEL_MAP as $value => $log_level) {
+            if (
+                $this->env !== GLPI::ENV_DEVELOPMENT
+                && in_array($log_level, [LogLevel::DEBUG, LogLevel::INFO])
+            ) {
+                // Do not report debug and info messages unless in development env.
+                // Suppressing the INFO level will prevent deprecations to be pushed in other environments logs.
+                //
+                // Suppressing the deprecations in the testing environment is mandatory to prevent deprecations
+                // triggered in vendor code to make our test suite fail.
+                // We may review this part once we will have migrate all our test suite on PHPUnit.
+                // For now, we rely on PHPStan to detect usages of deprecated code.
+                $reporting_level = $reporting_level & ~$value;
+            }
+
+            if (
+                !in_array($this->env, [GLPI::ENV_DEVELOPMENT, GLPI::ENV_TESTING], true)
+                && $log_level === LogLevel::NOTICE
+            ) {
+                // Do not report notice messages unless in development/testing env.
+                // Notices are errors with no functional impact, so we do not want people to report them as issues.
+                $reporting_level = $reporting_level & ~$value;
+            }
+        }
+        error_reporting($reporting_level);
 
         // Disable native error displaying as it will be handled by `self::outputDebugMessage()`.
         ini_set('display_errors', 'Off');
@@ -435,15 +460,6 @@ private function outputDebugMessage(string $error_type, string $message, string
             return;
         }
 
-        if (
-            in_array($this->env, [GLPI::ENV_STAGING, GLPI::ENV_PRODUCTION])
-            && in_array($log_level, [LogLevel::DEBUG, LogLevel::INFO])
-        ) {
-            // On staging/production environment, do not output debug/info messages.
-            // These messages are not supposed to be intended for end users, as they have no functional impact.
-            return;
-        }
-
         $is_dev_env         = $this->env === GLPI::ENV_DEVELOPMENT;
         $is_debug_mode      = isset($_SESSION['glpi_use_mode']) && $_SESSION['glpi_use_mode'] == \Session::DEBUG_MODE;
         $is_console_context = $this->output_handler instanceof OutputInterface;
@@ -513,7 +529,7 @@ private function codeToString(int $error_code): string
             E_USER_ERROR        => 'User Error',
             E_USER_WARNING      => 'User Warning',
             E_USER_NOTICE       => 'User Notice',
-            E_STRICT            => 'Runtime Notice',
+            2048                => 'Runtime Notice', // 2048 = deprecated E_STRICT
             E_RECOVERABLE_ERROR => 'Catchable Fatal Error',
             E_DEPRECATED        => 'Deprecated function',
             E_USER_DEPRECATED   => 'User deprecated function',
diff --git a/src/Glpi/Asset/Asset_PeripheralAsset.php b/src/Glpi/Asset/Asset_PeripheralAsset.php
index 50a907a8431..50f8f30ad23 100644
--- a/src/Glpi/Asset/Asset_PeripheralAsset.php
+++ b/src/Glpi/Asset/Asset_PeripheralAsset.php
@@ -258,7 +258,7 @@ public static function getMassiveActionsForItemtype(
         array &$actions,
         $itemtype,
         $is_deleted = false,
-        CommonDBTM $checkitem = null
+        ?CommonDBTM $checkitem = null
     ) {
         $action_prefix = __CLASS__ . MassiveAction::CLASS_ACTION_SEPARATOR;
         $specificities = self::getRelationMassiveActionsSpecificities();
diff --git a/src/Glpi/DBAL/QueryFunction.php b/src/Glpi/DBAL/QueryFunction.php
index 0e0ddf61ccf..6703e4bbbbc 100644
--- a/src/Glpi/DBAL/QueryFunction.php
+++ b/src/Glpi/DBAL/QueryFunction.php
@@ -175,7 +175,7 @@ public static function ifnull(string|QueryExpression $expression, string|QueryEx
      * @param string|null $alias Function result alias (will be automatically quoted)
      * @return QueryExpression
      */
-    public static function groupConcat(string|QueryExpression $expression, ?string $separator = null, bool $distinct = false, array|string $order_by = null, ?string $alias = null): QueryExpression
+    public static function groupConcat(string|QueryExpression $expression, ?string $separator = null, bool $distinct = false, array|string|null $order_by = null, ?string $alias = null): QueryExpression
     {
         /** @var \DBmysql $DB */
         global $DB;
@@ -309,7 +309,7 @@ public static function replace(string|QueryExpression $expression, string|QueryE
      * @param string|null $alias Function result alias (will be automatically quoted)
      * @return QueryExpression
      */
-    public static function fromUnixtime(string|QueryExpression $expression, string|QueryExpression $format = null, ?string $alias = null): QueryExpression
+    public static function fromUnixtime(string|QueryExpression $expression, string|QueryExpression|null $format = null, ?string $alias = null): QueryExpression
     {
         $params = [$expression];
         if ($format !== null) {
@@ -433,7 +433,7 @@ public static function timediff(string|QueryExpression $expression1, string|Quer
      * @param string|null $alias Function result alias (will be automatically quoted)
      * @return QueryExpression
      */
-    public static function unixTimestamp(string|QueryExpression $expression = null, ?string $alias = null): QueryExpression
+    public static function unixTimestamp(string|QueryExpression|null $expression = null, ?string $alias = null): QueryExpression
     {
         $params = [];
         if ($expression !== null) {
diff --git a/src/Glpi/Dashboard/FakeProvider.php b/src/Glpi/Dashboard/FakeProvider.php
index 398787c9180..c70a5ddb971 100644
--- a/src/Glpi/Dashboard/FakeProvider.php
+++ b/src/Glpi/Dashboard/FakeProvider.php
@@ -125,7 +125,7 @@ private static function getItemCount(?string $itemtype = null)
         return $values[$itemtype] ?? null;
     }
 
-    public static function bigNumberItem(CommonDBTM $item = null, array $params = []): array
+    public static function bigNumberItem(?CommonDBTM $item = null, array $params = []): array
     {
         return [
             'number' => self::getItemCount($item::class) ?? 1500,
@@ -278,7 +278,7 @@ public static function nbTicketsByAgreementStatusAndTechnicianGroup(array $param
         ];
     }
 
-    public static function nbItemByFk(CommonDBTM $item = null, CommonDBTM $fk_item = null, array $params = []): array
+    public static function nbItemByFk(?CommonDBTM $item = null, ?CommonDBTM $fk_item = null, array $params = []): array
     {
         $item_counts = self::getItemCount();
         $number_fk = $item_counts[$fk_item::class] ?? 20;
@@ -306,7 +306,7 @@ public static function nbItemByFk(CommonDBTM $item = null, CommonDBTM $fk_item =
         ];
     }
 
-    public static function articleListItem(CommonDBTM $item = null, array $params = []): array
+    public static function articleListItem(?CommonDBTM $item = null, array $params = []): array
     {
         $data = [];
         for ($i = 0; $i < 5; $i++) {
diff --git a/src/Glpi/Features/State.php b/src/Glpi/Features/State.php
index ede86e18a26..88776e4fb09 100644
--- a/src/Glpi/Features/State.php
+++ b/src/Glpi/Features/State.php
@@ -50,12 +50,11 @@ private function checkSetup(): void
         global $CFG_GLPI;
 
         if (!in_array(static::class, $CFG_GLPI['state_types'])) {
-            trigger_error(
+            throw new \LogicException(
                 sprintf(
                     'Class %s must be present in $CFG_GLPI[\'state_types\']',
                     static::class
-                ),
-                E_USER_ERROR
+                )
             );
         }
     }
diff --git a/src/Glpi/Form/ServiceCatalog/ServiceCatalogManager.php b/src/Glpi/Form/ServiceCatalog/ServiceCatalogManager.php
index 9b6f33da582..a88453c0976 100644
--- a/src/Glpi/Form/ServiceCatalog/ServiceCatalogManager.php
+++ b/src/Glpi/Form/ServiceCatalog/ServiceCatalogManager.php
@@ -161,7 +161,7 @@ function (ServiceCatalogItemInterface $item) use ($item_request) {
 
     private function hasChildren(
         ItemRequest $item_request,
-        ServiceCatalogCompositeInterface $composite = null,
+        ?ServiceCatalogCompositeInterface $composite = null,
     ): bool {
         $leaf_providers = array_filter(
             $this->providers,
diff --git a/src/Glpi/Marketplace/Controller.php b/src/Glpi/Marketplace/Controller.php
index ccae020c033..a4e9b532fec 100644
--- a/src/Glpi/Marketplace/Controller.php
+++ b/src/Glpi/Marketplace/Controller.php
@@ -159,7 +159,7 @@ private static function getPluginVersionInfo(array $plugin, string $version): ?a
      * @param ?string $version Download a specific version of the plugin
      * @return bool
      */
-    public function downloadPlugin($auto_install = true, string $version = null): bool
+    public function downloadPlugin($auto_install = true, ?string $version = null): bool
     {
         if (!self::hasWriteAccess()) {
             return false;
@@ -464,7 +464,7 @@ public function getRequiredOffers(): array
      *
      * @return bool
      */
-    public function canBeDownloaded(string $version = null)
+    public function canBeDownloaded(?string $version = null)
     {
         $api        = self::getAPI();
         $api_plugin = $api->getPlugin($this->plugin_key);
diff --git a/src/Glpi/System/Log/LogParser.php b/src/Glpi/System/Log/LogParser.php
index afb3fc4af5b..fff81594eb9 100644
--- a/src/Glpi/System/Log/LogParser.php
+++ b/src/Glpi/System/Log/LogParser.php
@@ -124,7 +124,7 @@ public function getLogFileInfo(string $filepath): ?array
      *
      * @return array|null
      */
-    public function parseLogFile(string $filepath, int $max_nb_lines = null): ?array
+    public function parseLogFile(string $filepath, ?int $max_nb_lines = null): ?array
     {
         /** @var array $CFG_GLPI */
         global $CFG_GLPI;
diff --git a/src/IPAddress.php b/src/IPAddress.php
index a02d3af9b5f..9439743ff25 100644
--- a/src/IPAddress.php
+++ b/src/IPAddress.php
@@ -1276,9 +1276,9 @@ private static function getCriteriaLinkedToNetwork(IPNetwork $network): array
      * @param array $options
      **/
     public static function getHTMLTableCellsForItem(
-        HTMLTableRow $row = null,
-        CommonDBTM $item = null,
-        HTMLTableCell $father = null,
+        ?HTMLTableRow $row = null,
+        ?CommonDBTM $item = null,
+        ?HTMLTableCell $father = null,
         array $options = []
     ) {
         /** @var \DBmysql $DB */
diff --git a/src/Line.php b/src/Line.php
index 0915e05bbcd..ebf085e5df7 100644
--- a/src/Line.php
+++ b/src/Line.php
@@ -246,7 +246,7 @@ public static function getIcon()
         return "ti ti-phone-calling";
     }
 
-    public static function getMassiveActionsForItemtype(array &$actions, $itemtype, $is_deleted = 0, CommonDBTM $checkitem = null)
+    public static function getMassiveActionsForItemtype(array &$actions, $itemtype, $is_deleted = 0, ?CommonDBTM $checkitem = null)
     {
         /** @var array $CFG_GLPI */
         global $CFG_GLPI;
diff --git a/src/QueuedWebhook.php b/src/QueuedWebhook.php
index 466c20e9250..91e1bcfa481 100644
--- a/src/QueuedWebhook.php
+++ b/src/QueuedWebhook.php
@@ -563,7 +563,7 @@ public static function getPendings($send_time = null, $limit = 20, $extra_where
      *
      * @return integer either 0 or 1
      **/
-    public static function cronQueuedWebhook(CronTask $task = null)
+    public static function cronQueuedWebhook(?CronTask $task = null)
     {
         $cron_status = 0;
 
@@ -589,7 +589,7 @@ public static function cronQueuedWebhook(CronTask $task = null)
      *
      * @return integer either 0 or 1
      **/
-    public static function cronQueuedWebhookClean(CronTask $task = null)
+    public static function cronQueuedWebhookClean(?CronTask $task = null)
     {
         /** @var \DBmysql $DB */
         global $DB;
diff --git a/src/Reservation.php b/src/Reservation.php
index be3fcccef7d..6642529d841 100644
--- a/src/Reservation.php
+++ b/src/Reservation.php
@@ -1153,7 +1153,7 @@ public static function getIcon()
         return "ti ti-calendar-event";
     }
 
-    public static function getMassiveActionsForItemtype(array &$actions, $itemtype, $is_deleted = 0, CommonDBTM $checkitem = null)
+    public static function getMassiveActionsForItemtype(array &$actions, $itemtype, $is_deleted = 0, ?CommonDBTM $checkitem = null)
     {
         /** @var array $CFG_GLPI */
         global $CFG_GLPI;
diff --git a/src/Toolbox.php b/src/Toolbox.php
index 9b2c57bcbcf..24abda6985f 100644
--- a/src/Toolbox.php
+++ b/src/Toolbox.php
@@ -262,7 +262,7 @@ public static function decodeFromUtf8($string, $to_charset = "ISO-8859-1")
      *
      * @return void
      **/
-    private static function log(LoggerInterface $logger = null, $level = LogLevel::WARNING, $args = null)
+    private static function log(?LoggerInterface $logger = null, $level = LogLevel::WARNING, $args = null)
     {
         static $tps = 0;
 
diff --git a/src/autoload/constants.php b/src/autoload/constants.php
index e8ec0791909..d737740f34e 100644
--- a/src/autoload/constants.php
+++ b/src/autoload/constants.php
@@ -45,7 +45,7 @@
 );
 
 define('GLPI_MIN_PHP', '8.2'); // Must also be changed in top of public/index.php
-define('GLPI_MAX_PHP', '8.3'); // Must also be changed in top of public/index.php
+define('GLPI_MAX_PHP', '8.4'); // Must also be changed in top of public/index.php
 define('GLPI_YEAR', '2024');
 
 //Define a global recipient address for email notifications
diff --git a/tests/functional/DBmysqlIterator.php b/tests/functional/DBmysqlIterator.php
index a7dde31ee69..ad9715e904b 100644
--- a/tests/functional/DBmysqlIterator.php
+++ b/tests/functional/DBmysqlIterator.php
@@ -1635,7 +1635,9 @@ public function testConvertOldRequestArgsToCriteria(array $params, array $expect
         $result = null;
         $this->when(
             function () use ($iterator, $params, &$result) {
+                $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
                 $result = $this->callPrivateMethod($iterator, 'convertOldRequestArgsToCriteria', $params, 'test');
+                \error_reporting($reporting_level); // restore previous level
             }
         )
          ->error
@@ -1665,7 +1667,9 @@ public function testExecuteWithOldSignature(array $params, array $expected, stri
         $iterator = new \DBmysqlIterator($db);
         $this->when(
             function () use ($iterator, $params) {
+                $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
                 $iterator = $iterator->execute(...$params);
+                \error_reporting($reporting_level); // restore previous level
             }
         )
          ->error
@@ -1701,7 +1705,9 @@ public function testBuildQueryWithOldSignature(array $params, array $expected, s
         $iterator = new \DBmysqlIterator($db);
         $this->when(
             function () use ($iterator, $params) {
+                $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
                 $iterator = $iterator->buildQuery(...$params);
+                \error_reporting($reporting_level); // restore previous level
             }
         )
          ->error
diff --git a/tests/functional/Glpi/Application/ErrorHandler.php b/tests/functional/Glpi/Application/ErrorHandler.php
index d59840bf776..ad35b5c065b 100644
--- a/tests/functional/Glpi/Application/ErrorHandler.php
+++ b/tests/functional/Glpi/Application/ErrorHandler.php
@@ -52,6 +52,9 @@ protected function errorProvider(): iterable
 
         foreach ([Session::NORMAL_MODE, Session::DEBUG_MODE] as $session_mode) {
             foreach ([GLPI::ENV_DEVELOPMENT, GLPI::ENV_TESTING, GLPI::ENV_STAGING, GLPI::ENV_PRODUCTION] as $env) {
+                $suppress_info   = $env !== GLPI::ENV_DEVELOPMENT;
+                $suppress_notice = !in_array($env, [GLPI::ENV_DEVELOPMENT, GLPI::ENV_TESTING], true);
+
                 yield [
                     'session_mode'         => $session_mode,
                     'env'                  => $env,
@@ -82,8 +85,8 @@ protected function errorProvider(): iterable
                     'error_call'           => function () {
                         trigger_error('some notice', E_USER_NOTICE);
                     },
-                    'expected_log_level'   => Level::Notice,
-                    'expected_msg_pattern' => $log_prefix
+                    'expected_log_level'   => $suppress_notice ? null : Level::Notice,
+                    'expected_msg_pattern' => $suppress_notice ? null : $log_prefix
                         . preg_quote('PHP User Notice (' . E_USER_NOTICE . '): some notice', '/')
                         . $log_suffix,
                 ];
@@ -94,8 +97,8 @@ protected function errorProvider(): iterable
                     'error_call'           => function () {
                         trigger_error('this method is deprecated', E_USER_DEPRECATED);
                     },
-                    'expected_log_level'   => Level::Info,
-                    'expected_msg_pattern' => $log_prefix
+                    'expected_log_level'   => $suppress_info ? null : Level::Info,
+                    'expected_msg_pattern' => $suppress_info ? null : $log_prefix
                         . preg_quote('PHP User deprecated function (' . E_USER_DEPRECATED . '): this method is deprecated', '/')
                         . $log_suffix,
                 ];
@@ -107,8 +110,8 @@ protected function errorProvider(): iterable
                         $param = new \ReflectionParameter([\Config::class, 'getTypeName'], 0);
                         $param->isCallable();
                     },
-                    'expected_log_level'   => Level::Info,
-                    'expected_msg_pattern' => $log_prefix
+                    'expected_log_level'   => $suppress_info ? null : Level::Info,
+                    'expected_msg_pattern' => $suppress_info ? null : $log_prefix
                         . preg_quote('PHP Deprecated function (' . E_DEPRECATED . '): Method ReflectionParameter::isCallable() is deprecated', '/')
                         . $log_suffix,
                 ];
@@ -128,13 +131,13 @@ public function testRegisteredErrorHandler(
         int $session_mode,
         string $env,
         callable $error_call,
-        Level $expected_log_level,
-        string $expected_msg_pattern
+        ?Level $expected_log_level,
+        ?string $expected_msg_pattern
     ) {
         $handler = new TestHandler();
         $logger = $this->newMockInstance('Monolog\\Logger', null, null, ['test-logger', [$handler]]);
 
-        $previous_use_mode         = $_SESSION['glpi_use_mode'];
+        $previous_use_mode = $_SESSION['glpi_use_mode'];
 
         $error_handler = $this->callPrivateConstructor(
             \Glpi\Application\ErrorHandler::class,
@@ -154,15 +157,13 @@ public function testRegisteredErrorHandler(
         $_SESSION['glpi_use_mode'] = $session_mode;
         $error_call();
         $_SESSION['glpi_use_mode'] = $previous_use_mode;
-        $this->integer(count($handler->getRecords()))->isEqualTo(1);
-        $this->boolean($handler->hasRecordThatMatches($expected_msg_pattern, $expected_log_level));
-        if (
-            $env === GLPI::ENV_DEVELOPMENT
-            || (
-                $session_mode === Session::DEBUG_MODE
-                && ($expected_log_level->isHigherThan(Level::Info)  || !in_array($env, [GLPI::ENV_STAGING, GLPI::ENV_PRODUCTION]))
-            )
-        ) {
+        if ($expected_log_level !== null) {
+            $this->integer(count($handler->getRecords()))->isEqualTo(1);
+            $this->boolean($handler->hasRecordThatMatches($expected_msg_pattern, $expected_log_level));
+        } else {
+            $this->integer(count($handler->getRecords()))->isEqualTo(0);
+        }
+        if ($expected_msg_pattern !== null && ($env === GLPI::ENV_DEVELOPMENT || $session_mode === Session::DEBUG_MODE)) {
             $this->output->matches($expected_msg_pattern);
         } else {
             $this->output->isEmpty();
@@ -177,6 +178,9 @@ protected function handleErrorProvider(): iterable
 
         foreach ([Session::NORMAL_MODE, Session::DEBUG_MODE] as $session_mode) {
             foreach ([GLPI::ENV_DEVELOPMENT, GLPI::ENV_TESTING, GLPI::ENV_STAGING, GLPI::ENV_PRODUCTION] as $env) {
+                $suppress_info   = $env !== GLPI::ENV_DEVELOPMENT;
+                $suppress_notice = !in_array($env, [GLPI::ENV_DEVELOPMENT, GLPI::ENV_TESTING], true);
+
                 yield [
                     'session_mode'         => $session_mode,
                     'env'                  => $env,
@@ -190,8 +194,8 @@ protected function handleErrorProvider(): iterable
                     'session_mode'         => $session_mode,
                     'env'                  => $env,
                     'error_code'           => E_NOTICE,
-                    'expected_log_level'   => Level::Notice,
-                    'expected_msg_pattern' => $log_prefix . 'PHP Notice' . $log_suffix,
+                    'expected_log_level'   => $suppress_notice ? null : Level::Notice,
+                    'expected_msg_pattern' => $suppress_notice ? null : $log_prefix . 'PHP Notice' . $log_suffix,
                     'is_fatal_error'       => false,
                 ];
 
@@ -226,8 +230,8 @@ protected function handleErrorProvider(): iterable
                     'session_mode'         => $session_mode,
                     'env'                  => $env,
                     'error_code'           => E_USER_NOTICE,
-                    'expected_log_level'   => Level::Notice,
-                    'expected_msg_pattern' => $log_prefix . 'PHP User Notice' . $log_suffix,
+                    'expected_log_level'   => $suppress_notice ? null : Level::Notice,
+                    'expected_msg_pattern' => $suppress_notice ? null : $log_prefix . 'PHP User Notice' . $log_suffix,
                     'is_fatal_error'       => false,
                 ];
 
@@ -235,8 +239,8 @@ protected function handleErrorProvider(): iterable
                     'session_mode'         => $session_mode,
                     'env'                  => $env,
                     'error_code'           => E_DEPRECATED,
-                    'expected_log_level'   => Level::Info,
-                    'expected_msg_pattern' => $log_prefix . 'PHP Deprecated function' . $log_suffix,
+                    'expected_log_level'   => $suppress_info ? null : Level::Info,
+                    'expected_msg_pattern' => $suppress_info ? null : $log_prefix . 'PHP Deprecated function' . $log_suffix,
                     'is_fatal_error'       => false,
                 ];
 
@@ -244,8 +248,8 @@ protected function handleErrorProvider(): iterable
                     'session_mode'         => $session_mode,
                     'env'                  => $env,
                     'error_code'           => E_USER_DEPRECATED,
-                    'expected_log_level'   => Level::Info,
-                    'expected_msg_pattern' => $log_prefix . 'PHP User deprecated function' . $log_suffix,
+                    'expected_log_level'   => $suppress_info ? null : Level::Info,
+                    'expected_msg_pattern' => $suppress_info ? null : $log_prefix . 'PHP User deprecated function' . $log_suffix,
                     'is_fatal_error'       => false,
                 ];
             }
@@ -261,20 +265,21 @@ public function testHandleError(
         int $session_mode,
         string $env,
         int $error_code,
-        Level $expected_log_level,
-        string $expected_msg_pattern,
+        ?Level $expected_log_level,
+        ?string $expected_msg_pattern,
         bool $is_fatal_error
     ) {
         $handler = new TestHandler();
         $logger = $this->newMockInstance('Monolog\\Logger', null, null, ['test-logger', [$handler]]);
 
-        $previous_use_mode         = $_SESSION['glpi_use_mode'];
+        $previous_use_mode = $_SESSION['glpi_use_mode'];
 
         $error_handler = $this->callPrivateConstructor(
             \Glpi\Application\ErrorHandler::class,
             [$logger, $env]
         );
         $error_handler->setForwardToInternalHandler(false);
+        $error_handler->register();
 
         // Assert that nothing is logged when using '@' operator
         $_SESSION['glpi_use_mode'] = $session_mode;
@@ -305,16 +310,13 @@ public function testHandleError(
             $_SESSION['glpi_use_mode'] = $previous_use_mode;
         }
 
-        $this->integer(count($handler->getRecords()))->isEqualTo(1);
-        $this->boolean($handler->hasRecordThatMatches($expected_msg_pattern, $expected_log_level));
-
-        if (
-            $env === GLPI::ENV_DEVELOPMENT
-            || (
-                $session_mode === Session::DEBUG_MODE
-                && ($expected_log_level->isHigherThan(Level::Info)  || !in_array($env, [GLPI::ENV_STAGING, GLPI::ENV_PRODUCTION]))
-            )
-        ) {
+        if ($expected_log_level !== null) {
+            $this->integer(count($handler->getRecords()))->isEqualTo(1);
+            $this->boolean($handler->hasRecordThatMatches($expected_msg_pattern, $expected_log_level));
+        } else {
+            $this->integer(count($handler->getRecords()))->isEqualTo(0);
+        }
+        if ($expected_msg_pattern !== null && ($env === GLPI::ENV_DEVELOPMENT || $session_mode === Session::DEBUG_MODE)) {
             $this->output->matches($expected_msg_pattern);
         } else {
             $this->output->isEmpty();
diff --git a/tests/functional/Glpi/Http/LegacyAssetsListener.php b/tests/functional/Glpi/Http/LegacyAssetsListener.php
index 71a1a781739..56352fe78a8 100644
--- a/tests/functional/Glpi/Http/LegacyAssetsListener.php
+++ b/tests/functional/Glpi/Http/LegacyAssetsListener.php
@@ -594,7 +594,9 @@ public function testServeLegacyAssetsFromDeprecatedMarketplacePath(): void
         $response = null;
         $this->when(
             function () use ($request, &$response) {
+                $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
                 $response = $this->callPrivateMethod($this->testedInstance, 'serveLegacyAssets', $request);
+                \error_reporting($reporting_level); // restore previous level
             }
         )->error
             ->withMessage('Accessing the plugins resources from the `/marketplace/` path is deprecated. Use the `/plugins/` path instead.')
diff --git a/tests/functional/Glpi/Http/LegacyRouterListener.php b/tests/functional/Glpi/Http/LegacyRouterListener.php
index 649aea79ba4..9a54e960c61 100644
--- a/tests/functional/Glpi/Http/LegacyRouterListener.php
+++ b/tests/functional/Glpi/Http/LegacyRouterListener.php
@@ -594,7 +594,9 @@ public function testRunLegacyRouterFromDeprecatedMarketplacePath(): void
 
         $this->when(
             function () use ($event) {
+                $reporting_level = \error_reporting(E_ALL); // be sure to report deprecations
                 $this->testedInstance->onKernelRequest($event);
+                \error_reporting($reporting_level); // restore previous level
             }
         )->error
             ->withMessage('Accessing the plugins resources from the `/marketplace/` path is deprecated. Use the `/plugins/` path instead.')
diff --git a/tests/src/FormTesterTrait.php b/tests/src/FormTesterTrait.php
index 053a8110366..00ee9a0c36d 100644
--- a/tests/src/FormTesterTrait.php
+++ b/tests/src/FormTesterTrait.php
@@ -161,7 +161,7 @@ protected function createForm(FormBuilder $builder): Form
     protected function getQuestionId(
         Form $form,
         string $question_name,
-        string $section_name = null,
+        ?string $section_name = null,
     ): int {
         // Make sure form is up to date
         $form->getFromDB($form->getID());
@@ -239,7 +239,7 @@ protected function getSectionId(
     protected function getCommentId(
         Form $form,
         string $comment_name,
-        string $section_name = null,
+        ?string $section_name = null,
     ): int {
         // Make sure form is up to date
         $form->getFromDB($form->getID());
diff --git a/tools/patches/apereo-phpcas-php84.patch b/tools/patches/apereo-phpcas-php84.patch
new file mode 100644
index 00000000000..6df6e7d594c
--- /dev/null
+++ b/tools/patches/apereo-phpcas-php84.patch
@@ -0,0 +1,35 @@
+diff --git a/source/CAS.php b/source/CAS.php
+index df6bc82..da145bc 100644
+--- a/source/CAS.php
++++ b/source/CAS.php
+@@ -347,7 +347,7 @@ class phpCAS
+      */
+     public static function client($server_version, $server_hostname,
+         $server_port, $server_uri, $service_base_url,
+-        $changeSessionID = true, \SessionHandlerInterface $sessionHandler = null
++        $changeSessionID = true, ?\SessionHandlerInterface $sessionHandler = null
+     ) {
+         phpCAS :: traceBegin();
+         if (is_object(self::$_PHPCAS_CLIENT)) {
+@@ -402,7 +402,7 @@ class phpCAS
+      */
+     public static function proxy($server_version, $server_hostname,
+         $server_port, $server_uri, $service_base_url,
+-        $changeSessionID = true, \SessionHandlerInterface $sessionHandler = null
++        $changeSessionID = true, ?\SessionHandlerInterface $sessionHandler = null
+     ) {
+         phpCAS :: traceBegin();
+         if (is_object(self::$_PHPCAS_CLIENT)) {
+diff --git a/source/CAS/Client.php b/source/CAS/Client.php
+index 8ca9711..42709e9 100644
+--- a/source/CAS/Client.php
++++ b/source/CAS/Client.php
+@@ -938,7 +938,7 @@ class CAS_Client
+         $server_uri,
+         $service_base_url,
+         $changeSessionID = true,
+-        \SessionHandlerInterface $sessionHandler = null
++        ?\SessionHandlerInterface $sessionHandler = null
+     ) {
+         // Argument validation
+         if (gettype($server_version) != 'string')