Add first-draft GitHub Action (GHA) for PHPUnit.

Author: Potherca

.github/workflows/tests.php.unit.yml

@@ -0,0 +1,34 @@
+name: PHP Unit Tests
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        php-version:
+          - '5.5'
+          - '5.6'
+          - '7.0'
+        include:
+          - php-version: '7.0'
+            allow_failure: true
+    continue-on-error: ${{ matrix.allow_failure || false }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: shivammathur/setup-php@v2
+        with:
+          coverage: xdebug
+          extensions: gd, json, mbstring
+          php-version: ${{ matrix.php-version }}
+      - run: composer install --no-interaction --prefer-dist
+      - run: vendor/bin/phpunit
+      - uses: codecov/codecov-action@v5
+        if: success()
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+      - uses: coverallsapp/github-action@v2
+        if: success()