diff --git a/.github/workflows/phan.yml b/.github/workflows/phan.yml
new file mode 100644
index 0000000..957a3a0
--- /dev/null
+++ b/.github/workflows/phan.yml
@@ -0,0 +1,66 @@
+name: Phan
+
+permissions:
+  contents: read
+
+on:
+  push:
+    branches:
+      - "*"
+  pull_request:
+    branches: [ 'master', 'main' ]
+  pull_request_target:
+    types:
+      - closed
+
+jobs:
+  run:
+    name: Run Phan
+    runs-on: 'ubuntu-latest'
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@0f7f1d08e3e32076e51cae65eb0b0c871405b16e # v2.34.1
+        with:
+          php-version: '8.4'
+          tools: phan:5.5.0
+          coverage: none
+
+      - name: Restore cached baseline for Phan
+        id: cache-baseline-restore
+        uses: actions/cache/restore@d4323d4df104b026a6aa633fdb11d772146be0bf # v4.2.2
+        with:
+          path: |
+            test/phan-baseline.php
+          key: phan-baseline-${{ github.run_id }}"
+          restore-keys: |
+            phan-baseline-
+
+      - name: Run Phan
+        continue-on-error: true
+        run: |
+          if [ -f ~/test/phan-baseline.php ]; then
+            echo "Cached baseline for Phan is found. Running Phan with baseline."
+            phan -d ./ -k .phan/config.php --load-baseline ~/test/phan-baseline.php --no-progress-bar
+          else
+            echo "Cached baseline for Phan is not found. Running Phan without baseline."
+            phan -d ./ -k .phan/config.php --no-progress-bar
+            exit 0
+          fi
+
+      - name: Generate the baseline for Phan
+        continue-on-error: true
+        if: github.event.pull_request.merged == true
+        run: |
+          phan -d ./ -k .phan/config.php --save-baseline ~/test/phan-baseline.php --no-progress-bar
+          exit 0
+
+      - name: Save the baseline for Phan
+        id: save-the-baseline-for-phan
+        if: github.event.pull_request.merged == true
+        uses: actions/cache/save@d4323d4df104b026a6aa633fdb11d772146be0bf # v4.2.2
+        with:
+          path: |
+            test/phan-baseline.php
+          key: phan-baseline-${{ github.run_id }}"
diff --git a/.phan/config.php b/.phan/config.php
new file mode 100644
index 0000000..723cf11
--- /dev/null
+++ b/.phan/config.php
@@ -0,0 +1,14 @@
+<?php
+declare(strict_types=1);
+
+return [
+    'target_php_version' => '8.4',
+
+    'directory_list' => [
+        'src',
+    ],
+
+    'exclude_analysis_directory_list' => [
+        'vendor/'
+    ],
+];