Split PHPUnit tests into separate php-tests workflow; align PHP packages

- Move PHPUnit step from php-linter into new php-tests.yml
- All three workflows now install the same PHP packages:
  php-cli, php-mbstring, php-xml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: carlbennett

.github/workflows/deployment.yml

@@ -29,7 +29,7 @@ jobs:
         run: sudo apt-get update
 
       - name: Install PHP ${{ env.PHP_VERSION }}
-        run: sudo apt-get install php${{ env.PHP_VERSION }}-cli
+        run: sudo apt-get install php${{ env.PHP_VERSION }}-cli php${{ env.PHP_VERSION }}-mbstring php${{ env.PHP_VERSION }}-xml
 
       - name: Validate composer.json and composer.lock
         run: composer validate --strict

.github/workflows/php-linter.yml

@@ -47,6 +47,3 @@ jobs:
 
       - name: Validate PHP syntax
         run: bash -c 'set -e;for file in $(find ./src ./tests -type f -regex ".*\.\(php\|phtml\)" -print); do php -e -l -f "$file"; done'
-
-      - name: Run PHPUnit tests
-        run: lib/bin/phpunit --testdox

.github/workflows/php-tests.yml

@@ -0,0 +1,46 @@
+# vim: set colorcolumn=:
+name: php-tests
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+    inputs:
+      php_version:
+        description: "Specify the PHP version to use (e.g., 8.3)"
+        required: false
+        default: '8.3'
+
+env:
+  PHP_VERSION: ${{ inputs.php_version || '8.3' }}
+
+permissions:
+  contents: read
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Update apt cache
+        run: sudo apt-get update
+
+      - name: Install php ${{ env.PHP_VERSION }}
+        run: sudo apt-get install php${{ env.PHP_VERSION }}-cli php${{ env.PHP_VERSION }}-mbstring php${{ env.PHP_VERSION }}-xml
+
+      - name: Cache Composer packages
+        id: composer-cache
+        uses: actions/cache@v4
+        with:
+          path: lib
+          key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-php-
+
+      - name: Install composer/vendor dependencies
+        run: composer install --prefer-dist --no-progress --ignore-platform-reqs
+
+      - name: Run PHPUnit tests
+        run: lib/bin/phpunit --testdox