chore: use step env instead of global env

Author: kenjis

.github/workflows/phpunit.yml

@@ -18,9 +18,6 @@ on:
       - 'phpunit*'
       - '.github/workflows/phpunit.yml'
 
-env:
-  COMPOSER_UPDATE_FLAGS: ""
-
 jobs:
   main:
     name: PHP ${{ matrix.php-versions }} - ${{ matrix.db-platforms }} - ${{ matrix.dependencies }}
@@ -147,17 +144,15 @@ jobs:
           key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}-${{ hashFiles('**/composer.lock') }}
           restore-keys: ${{ runner.os }}-composer-
 
-      - name: Handle lowest dependencies update
-        if: contains(matrix.dependencies, 'lowest')
-        run: echo "COMPOSER_UPDATE_FLAGS=$COMPOSER_UPDATE_FLAGS --prefer-lowest" >> $GITHUB_ENV
-
       - name: Install dependencies
         run: |
           if [ -f composer.lock ]; then
             composer install ${{ env.COMPOSER_UPDATE_FLAGS }} --no-progress --no-interaction --prefer-dist --optimize-autoloader
           else
             composer update ${{ env.COMPOSER_UPDATE_FLAGS }} --no-progress --no-interaction --prefer-dist --optimize-autoloader
           fi
+        env:
+          COMPOSER_UPDATE_FLAGS: ${{ matrix.dependencies == 'lowest' && '--prefer-lowest' || '' }}
 
       - name: Test with PHPUnit
         run: vendor/bin/phpunit --verbose --coverage-text --testsuite main