diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 3f0673d..f511158 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -16,13 +16,11 @@ jobs:
         php_version:
           - '8.2'
           - '8.3'
-        dependencies:
+          - '8.4'
+        dependency-versions:
+          - 'lowest'
           - 'default'
-        include:
-          - php_version: '8.2'
-            dependencies: 'lowest'
-          - php_version: '8.3'
-            dependencies: 'lowest'
+
     steps:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
@@ -35,28 +33,10 @@ jobs:
         with:
           show-progress: false
 
-      - name: Get Composer Cache Directory
-        id: composer-cache
-        run: |
-          echo "::set-output name=dir::$(composer config cache-files-dir)"
-
-      - uses: actions/cache@v4
-        with:
-          path: ${{ steps.composer-cache.outputs.dir }}
-          key: ${{ runner.os }}-composer-${{ matrix.dependencies }}-${{ hashFiles('**/composer.lock') }}
-          restore-keys: |
-            ${{ runner.os }}-composer-${{ matrix.dependencies }}
-
       - name: Install composer dependencies
-        env:
-          DEPENDENCIES: ${{ matrix.dependencies }}
-        run: |
-          if [ $DEPENDENCIES == 'lowest' ]
-          then
-            composer update --prefer-lowest --no-interaction --no-progress
-          else
-            composer install --no-interaction --no-progress
-          fi
+        uses: ramsey/composer-install@v3
+        with:
+          dependency-versions: ${{ matrix.dependency-versions }}
 
       - name: Run unit tests
         run: |
diff --git a/CHANGELOG.md b/CHANGELOG.md
index bc07d26..72fd167 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ### Unreleased
 
+### v2.5.0 (2025-06-26)
+
+* Support PHP 8.4
+
 ### v2.4.0 (2025-06-05)
 
 * Fix `ObjectPropertyRipper` to handle `stdClass` objects
diff --git a/composer.json b/composer.json
index 873dc88..9cf80e3 100644
--- a/composer.json
+++ b/composer.json
@@ -16,15 +16,15 @@
   ],
   "require": {
     "ext-json": "*",
-    "ext-mbstring": "~8.2.0 || ~8.3.0",
-    "ext-pdo": "~8.2.0 || ~8.3.0",
-    "ext-sodium": "~8.2.0 || ~8.3.0",
-    "php": "~8.2.0 || ~8.3.0",
+    "ext-mbstring": "~8.2.0 || ~8.3.0 || ~8.4.0",
+    "ext-pdo": "~8.2.0 || ~8.3.0 || ~8.4.0",
+    "ext-sodium": "~8.2.0 || ~8.3.0 || ~8.4.0",
+    "php": "~8.2.0 || ~8.3.0 || ~8.4.0",
     "psr/log": "^1.1 || ^2.0 || ^3.0"
   },
   "require-dev": {
-    "mikey179/vfsstream": "^1.6.11",
-    "phpunit/phpunit": "^11.0",
+    "mikey179/vfsstream": "^1.6.12",
+    "phpunit/phpunit": "^11.5",
     "ergebnis/phpunit-slow-test-detector": "^2.15"
   },
   "support": {
diff --git a/src/DateTime/DateString.php b/src/DateTime/DateString.php
index 8fa4d46..059415e 100644
--- a/src/DateTime/DateString.php
+++ b/src/DateTime/DateString.php
@@ -22,7 +22,7 @@ class DateString
      *
      * @return string
      */
-    public static function format(\DateTimeImmutable $date = NULL, $format, $empty_value = '')
+    public static function format(?\DateTimeImmutable $date, $format, $empty_value = '')
     {
         if ( ! $date) {
             return $empty_value;
@@ -52,7 +52,7 @@ public static function isoMS(?\DateTimeImmutable $date, ?string $empty_value = '
      *
      * @return string
      */
-    public static function ymd(\DateTimeImmutable $date = NULL, $empty_value = '')
+    public static function ymd(?\DateTimeImmutable $date, $empty_value = '')
     {
         return static::format($date, 'Y-m-d', $empty_value);
     }
@@ -65,7 +65,7 @@ public static function ymd(\DateTimeImmutable $date = NULL, $empty_value = '')
      *
      * @return string
      */
-    public static function ymdhis(\DateTimeImmutable $date = NULL, $empty_value = '')
+    public static function ymdhis(?\DateTimeImmutable $date, $empty_value = '')
     {
         return static::format($date, 'Y-m-d H:i:s', $empty_value);
     }
diff --git a/src/DeploymentConfig/DeploymentConfig.php b/src/DeploymentConfig/DeploymentConfig.php
index 7d24655..cf57a67 100644
--- a/src/DeploymentConfig/DeploymentConfig.php
+++ b/src/DeploymentConfig/DeploymentConfig.php
@@ -58,7 +58,7 @@ public static function instance()
      *
      * @param array|NULL $env_vars - if missing will default to reading from $_SERVER
      */
-    protected function __construct(array $env_vars = NULL)
+    protected function __construct(?array $env_vars = NULL)
     {
         if ($env_vars === NULL) {
             $env_vars = $_SERVER;
diff --git a/src/Monitoring/OperationTimer.php b/src/Monitoring/OperationTimer.php
index 3ed2b97..28547c5 100644
--- a/src/Monitoring/OperationTimer.php
+++ b/src/Monitoring/OperationTimer.php
@@ -17,7 +17,7 @@ class OperationTimer
 
     protected RealtimeClock $realtime_clock;
 
-    public function __construct(MetricsAgent $metrics_agent, RealtimeClock $realtime_clock = NULL)
+    public function __construct(MetricsAgent $metrics_agent, ?RealtimeClock $realtime_clock = NULL)
     {
         $this->metrics_agent  = $metrics_agent;
         $this->realtime_clock = $realtime_clock ?? new RealtimeClock();
diff --git a/test/unit/CSV/CSVWriterTest.php b/test/unit/CSV/CSVWriterTest.php
index 899f1ef..61dfb98 100644
--- a/test/unit/CSV/CSVWriterTest.php
+++ b/test/unit/CSV/CSVWriterTest.php
@@ -248,7 +248,7 @@ public function test_it_optionally_writes_byte_order_mark_at_start_of_file($writ
         if ($write_bom) {
             $this->assertSame(CSVWriter::UTF8_BOM, fread($file, strlen(CSVWriter::UTF8_BOM)));
         }
-        $this->assertSame(['first'], fgetcsv($file));
+        $this->assertSame(['first'], fgetcsv($file, escape: '\\'));
     }
 
     #[TestWith([['is' => 'jumbled', 'our' => 'up']])]
@@ -284,7 +284,7 @@ protected function assertCSVContent(array $expect, $file)
     {
         rewind($file);
         $actual = [];
-        while ($row = fgetcsv($file)) {
+        while ($row = fgetcsv($file, escape: '\\')) {
             $actual[] = $row;
         }
 
diff --git a/test/unit/Logging/ExternalCallSiteFinderTest.php b/test/unit/Logging/ExternalCallSiteFinderTest.php
index 4583f1f..22f46a4 100644
--- a/test/unit/Logging/ExternalCallSiteFinderTest.php
+++ b/test/unit/Logging/ExternalCallSiteFinderTest.php
@@ -129,8 +129,20 @@ function log_ab8123723123($asserter) {
             [
                 <<<'PHP'
                 // Anonymous func
+                use test\unit\Ingenerator\PHPUtils\Logging\ExternalCallSiteFinderTest;
                 return (function ($asserter) {
-                    return $asserter->test(['file' => __FILE__, 'line' => __LINE__, 'function' => '{closure}']);
+                    if (PHP_VERSION_ID < 80400) {
+                        $expected_func_name = '{closure}';
+                    } else {
+                        $expected_func_name = sprintf("%s->{closure:%s:%d}",
+                            ExternalCallSiteFinderTest::class,
+                            __FILE__,
+                            // it's the line with the 'function' keyword
+                            (__LINE__-8)
+                        );
+                    }
+                    return $asserter->test(['file' => __FILE__, 'line' => __LINE__, 'function' => $expected_func_name]);
+                    
                 })($asserter);
 PHP
                 ,
diff --git a/test/unit/Mutex/BasicPDOStatementStub.php b/test/unit/Mutex/BasicPDOStatementStub.php
index ad45199..9a05926 100644
--- a/test/unit/Mutex/BasicPDOStatementStub.php
+++ b/test/unit/Mutex/BasicPDOStatementStub.php
@@ -38,20 +38,8 @@ class BasicPDOStatementStub extends \PDOStatement
 
         public function __construct(array $result) { $this->result = $result; }
 
-        public function fetchAll(int $fetch_style = NULL, mixed ...$fetch_argument): array
+        public function fetchAll(?int $fetch_style = NULL, mixed ...$fetch_argument): array
         {
-            if (PHP_VERSION_ID < 80100) {
-                // Before 8.1, ints and floats were returned as strings
-                // https://www.php.net/manual/en/migration81.incompatible.php#migration81.incompatible.pdo.mysql
-                $this->result = array_map(
-                    fn($row) => array_map(
-                        fn($column) => (is_int($column) || \is_float($column)) ? (string) $column : $column,
-                        $row
-                    ),
-                    $this->result
-                );
-            }
-
             if ($fetch_style === NULL) {
                 return $this->result;
             } elseif ($fetch_style === PDO::FETCH_COLUMN) {