Run conformance tests in regular linux build

.github/workflows/test_php.yml

@@ -77,6 +77,15 @@ jobs:
           extra-flags: -e COMPOSER_HOME=/workspace/composer-cache
           command: ${{ matrix.command }}
 
+      - name: Run conformance tests
+        if: ${{ !matrix.continuous-only || inputs.continuous-run }}
+        uses: protocolbuffers/protobuf-ci/bazel@v3
+        with:
+          image: us-docker.pkg.dev/protobuf-build/containers/test/linux/php:6.4.0-${{ matrix.version }}-27cf7b86212020d7e552bc13b1e084abb971da75
+          credentials: ${{ secrets.GAR_SERVICE_ACCOUNT }}
+          bazel-cache: php_linux/${{ matrix.version }}
+          bazel: test //php:conformance_test //php:conformance_test_c --action_env=PATH --test_env=PATH
+
   linux-32bit:
     strategy:
       fail-fast: false   # Don't cancel all jobs if one fails.