added DISPLAY env and xvfb for 5.3

Author: oleg-andreyev

.travis.yml

@@ -14,6 +14,10 @@ services:
 #  - 7.2
 #  - 7.3
 
+env:
+  global:
+    - DISPLAY=:99.0
+
 cache:
   directories:
     - $HOME/.composer/cache/files
@@ -32,6 +36,7 @@ before_script:
   - |
     if [[ ${TRAVIS_PHP_VERSION:0:3} == "5.3" ]]; then
       wget http://selenium-release.storage.googleapis.com/2.53/selenium-server-standalone-2.53.1.jar
+      sh -e /etc/init.d/xvfb start
       java -jar selenium-server-standalone-2.53.1.jar &
     else
       docker run -p 4444:4444 --network=host -v /dev/shm:/dev/shm --shm-size 2g selenium/standalone-firefox:2.53.1 &> ./logs/selenium.log &