Add hhvm to Travis CI configuration

.travis.yml

@@ -27,12 +27,14 @@ php:
   - 5.5
   - 5.6
   - 7
+  - hhvm
 
 matrix:
   fast_finish: true
 
   allow_failures:
     - php: 7
+    - php: hhvm
 
 before_install:
   - travis_retry composer self-update -n
@@ -41,12 +43,9 @@ install:
   - travis_retry composer install -n --prefer-dist
 
 before_script:
-  - cp tests/travis/mysql.ini tests/configs/mysql.ini
-  - cp tests/travis/pgsql.ini tests/configs/pgsql.ini
-  - cp tests/travis/sqlite.ini tests/configs/sqlite.ini
-  - mysql -u root -e 'create database midas_test;'
-  - psql -U postgres -c 'create database midas_test;'
-  - touch midas_test.db
+  - cp tests/travis/mysql.ini tests/configs/mysql.ini && mysql -u root -e 'create database midas_test;'
+  - if [[ $TRAVIS_PHP_VERSION != hhvm ]]; then cp tests/travis/pgsql.ini tests/configs/pgsql.ini && psql -U postgres -c 'create database midas_test;'; fi
+  - cp tests/travis/sqlite.ini tests/configs/sqlite.ini && touch midas_test.db
 
 script:
   - mkdir _test && cd _test