diff --git a/.github/workflows/phpmd.yml b/.github/workflows/phpmd.yml
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+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+# PHPMD is a spin-off project of PHP Depend and 
+# aims to be a PHP equivalent of the well known Java tool PMD.
+# What PHPMD does is: It takes a given PHP source code base 
+# and look for several potential problems within that source.
+# These problems can be things like:
+#   Possible bugs
+#   Suboptimal code
+#   Overcomplicated expressions
+#   Unused parameters, methods, properties
+# More details at https://phpmd.org/
+
+name: PHPMD
+
+on:
+  push:
+    branches: [ "4.0.x", "*.*.x" ]
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [ "4.0.x" ]
+  schedule:
+    - cron: '40 12 * * 2'
+
+permissions:
+  contents: read
+
+jobs:
+  PHPMD:
+    name: Run PHPMD scanning
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read # for checkout to fetch code
+      security-events: write # for github/codeql-action/upload-sarif to upload SARIF results
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@aa1fe473f9c687b6fb896056d771232c0bc41161
+        with:
+          coverage: none
+          tools: phpmd
+
+      - name: Run PHPMD
+        run: phpmd . sarif codesize --reportfile phpmd-results.sarif
+        continue-on-error: true
+
+      - name: Upload analysis results to GitHub
+        uses: github/codeql-action/upload-sarif@v2
+        with:
+          sarif_file: phpmd-results.sarif
+          wait-for-processing: true