Update the test workflow to match XRay's and run the integration tests

Test on PHP 7.2 through 8.4, up from 8.0, and update the checkout and
cache actions to v4. Key the cache on the PHP version and composer.json:
there's no committed composer.lock, so every matrix job was sharing one
vendor cache. Add a Redis service and run the integration suite too,
which the workflow never ran.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.github/workflows/php.yml

@@ -10,11 +10,24 @@ jobs:
   build:
     strategy:
       matrix:
-        php-versions: ["7.2", "7.3", "7.4", "8.0"]
+        # The library supports PHP 5.5+, but PHPUnit 8.5 needs 7.2 or later
+        php-versions: ["7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3", "8.4"]
     runs-on: ubuntu-latest
 
+    # The integration tests use Redis on 127.0.0.1:6379
+    services:
+      redis:
+        image: redis
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 10
+
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
 
       - name: Setup PHP, with composer and extensions
         uses: shivammathur/setup-php@v2 #https://github.com/shivammathur/setup-php
@@ -23,20 +36,24 @@ jobs:
           extensions: mbstring, simplexml, dom, curl
           coverage: pcov
 
-      - name: Validate composer.json and composer.lock
+      - name: Validate composer.json
         run: composer validate --strict
 
       - name: Cache Composer packages
         id: composer-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: vendor
-          key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+          key: ${{ runner.os }}-php-${{ matrix.php-versions }}-${{ hashFiles('composer.json') }}
           restore-keys: |
-            ${{ runner.os }}-php-
-            
+            ${{ runner.os }}-php-${{ matrix.php-versions }}-
+
+      # There's no committed composer.lock, so resolve for each PHP version
       - name: Install dependencies
         run: composer update --prefer-dist --no-progress
 
-      - name: Run test suite
+      - name: Run unit tests
         run: composer run-script test
+
+      - name: Run integration tests
+        run: vendor/bin/phpunit --testsuite integration