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/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/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/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')