test against php 8

.travis.yml

@@ -1,26 +1,29 @@
+dist: bionic
+
 language: php
 
 matrix:
   include:
     - php: 7.2
-      env: dependencies=lowest
+      env: composerargs="--prefer-lowest"
     - php: 7.2
     - php: 7.3
-      env: dependencies=lowest
+      env: composerargs="--prefer-lowest"
     - php: 7.3
     - php: 7.4
-      env: dependencies=lowest
+      env: composerargs="--prefer-lowest"
     - php: 7.4
+    - php: nightly
+      env: composerargs="--ignore-platform-reqs"
+  allow_failures:
+    - php: nightly
 
 before_script:
-  - rm ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/xdebug.ini
-  - echo 'extension=apcu.so' >> ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/apcu.ini
   - echo 'Europe/Zurich' | sudo tee /etc/timezone
   - echo 'date.timezone = "Europe/Zurich"' >> ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/travis.ini
   - composer self-update -q
   - composer global require hirak/prestissimo
-  - if [ -z "$dependencies" ]; then composer update -n; fi;
-  - if [ "$dependencies" = "lowest" ]; then composer update --prefer-lowest -n; fi;
+  - composer update $composerargs -n
 
 script:
   - composer test