Test Symfony version 2, 3 and 4 with different versions of php. (#5)

.gitignore

@@ -1,3 +1,3 @@
 .DS_Store
 vendor
-composer.lock
+build

.travis.yml

@@ -6,10 +6,18 @@ branches:
     - master
     - /^[[:digit:]]+\.[[:digit:]]+\.[[:digit:]]+.*$/
 
-php:
-  - 5.5
-  - 5.6
-  - 7.0
+matrix:
+  include:
+    -
+      php: 7.1
+      env: 'HIGHEST_LOWEST="update" STABILITY="RC"'
+    -
+      php: 7.0.11
+    -
+      php: 5.6
+    -
+      php: 5.5
+      env: 'HIGHEST_LOWEST="update --prefer-lowest"'
 
 sudo: false
 
@@ -19,7 +27,17 @@ cache:
     - $HOME/.composer/cache
 
 before_script:
-  - composer install
+  # If running a highest/lowest dependencies test, get rid of composer.lock
+  - |
+    if [ -n "$HIGHEST_LOWEST" ] ; then
+      rm composer.lock
+      composer config --unset platform.php
+      composer config minimum-stability ${STABILITY-stable}
+    fi
+  - 'composer -n ${HIGHEST_LOWEST-install} --prefer-dist'
+  - composer why symfony/console
+  # Print out all  of the installed packages in alphabetical order, with versions
+  - composer licenses
 
 script:
   - vendor/bin/phpcs --standard=PSR2 -n src

composer.json

@@ -21,16 +21,22 @@
     "require": {
         "php": ">=5.5.0",
         "psr/log": "~1.0",
-        "symfony/console": "~2.5|~3.0|~4.0"
+        "symfony/console": "^2.8|^3|^4"
     },
     "require-dev": {
         "phpunit/phpunit": "4.*",
-        "satooshi/php-coveralls": "^1.0",
+        "satooshi/php-coveralls": "dev-master",
         "squizlabs/php_codesniffer": "2.*"
     },
+    "minimum-stability": "stable",
     "extra": {
         "branch-alias": {
             "dev-master": "1.x-dev"
         }
+    },
+    "config": {
+        "platform": {
+            "php": "5.6"
+        }
     }
 }