Merge #16743 - Add PHP 8.1 to the CI matrix

Signed-off-by: William Desportes <williamdes@wdes.fr>

.github/workflows/tests.yml

@@ -13,10 +13,14 @@ jobs:
         name: Test on php ${{ matrix.php-version }} and ${{ matrix.os }}
         if: "!contains(github.event.head_commit.message, '[ci skip]')"
         runs-on: ${{ matrix.os }}
+        continue-on-error: ${{ matrix.experimental }}
         strategy:
             matrix:
                 php-version: ["7.1", "7.2", "7.3", "7.4", "8.0"]
+                experimental: [false]
                 os: [ubuntu-latest]
+                include:
+                    - { php-version: '8.1', composer-options: '--ignore-platform-req=php', experimental: true, os: ubuntu-latest }
         steps:
             - uses: actions/checkout@v2
             - name: Install gettext
@@ -35,7 +39,7 @@ jobs:
                   path: ~/.composer/cache/
                   key: composer-cache
             - name: Install dependencies
-              run: composer install --no-interaction
+              run: composer install --no-interaction ${{ matrix.composer-options }}
             - name: Run php tests
               run: composer run phpunit --  --exclude-group selenium
             - name: Send coverage