GH Actions: various updates

1. Start running tests against PHP 8.4 (expected to be released end of November).
2. Update the `actions/checkout` action runner.
3. Update the `ramsey/composer-install` action runner.
4. Fix an outdated link.

.github/workflows/test.yml

@@ -18,15 +18,15 @@ jobs:
 
  strategy:
  matrix:
- php: ['5.3', '5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3']
+ php: ['5.3', '5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
- continue-on-error: ${{ matrix.php == '8.3' }}
+ continue-on-error: ${{ matrix.php == '8.4' }}
 
  name: "Test: PHP ${{ matrix.php }}"
 
  steps:
  - name: Checkout code
- uses: actions/checkout@v3
+ uses: actions/checkout@v4
 
  - name: Install PHP
  uses: shivammathur/setup-php@v2
@@ -43,15 +43,15 @@ jobs:
 
  strategy:
  matrix:
- php: ['5.3', '5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3']
+ php: ['5.3', '5.4', '5.5', '5.6', '7.0', '7.1', '7.2', '7.3', '7.4', '8.0', '8.1', '8.2', '8.3', '8.4']
 
- continue-on-error: ${{ matrix.php == '8.3' }}
+ continue-on-error: ${{ matrix.php == '8.4' }}
 
  name: "Unit Test: PHP ${{ matrix.php }}"
 
  steps:
  - name: Checkout code
- uses: actions/checkout@v3
+ uses: actions/checkout@v4
 
  - name: Install PHP
  uses: shivammathur/setup-php@v2
@@ -61,17 +61,17 @@ jobs:
  coverage: xdebug
 
  # Install dependencies and handle caching in one go.
- # @link https://github.com/marketplace/actions/install-composer-dependencies
+ # @link https://github.com/marketplace/actions/install-php-dependencies-with-composer
  - name: Install Composer dependencies - normal
- if: ${{ matrix.php != '8.3' }}
- uses: "ramsey/composer-install@v2"
+ if: ${{ matrix.php != '8.4' }}
+ uses: "ramsey/composer-install@v3"
  with:
  # Bust the cache at least once a month - output format: YYYY-MM.
  custom-cache-suffix: $(date -u "+%Y-%m")
 
  - name: Install Composer dependencies - ignore PHP restrictions
- if: ${{ matrix.php == '8.3' }}
- uses: "ramsey/composer-install@v2"
+ if: ${{ matrix.php == '8.4' }}
+ uses: "ramsey/composer-install@v3"
  with:
  composer-options: --ignore-platform-req=php+
  # Bust the cache at least once a month - output format: YYYY-MM.