Allow installation on PHP 8

.travis.yml

@@ -77,6 +77,13 @@ jobs:
       dist: precise
       env: PHPCS_VERSION="2.0.0"
 
+    - php: nightly
+      env: PHPCS_VERSION="dev-master" LINT=1
+
+  allow_failures:
+    # Allow failures for unstable builds.
+    - php: "nightly"
+
   fast_finish: true
 
 before_install:
@@ -93,7 +100,13 @@ install:
       # Install PHPCompatibility 8.x for PHPCS 2.2 < 2.3.
       composer require --no-update --no-suggest --no-scripts phpcompatibility/php-compatibility:"^8.0"
     fi
-  - travis_wait composer install --no-interaction --no-progress --no-scripts --no-suggest --optimize-autoloader --prefer-dist --verbose
+  - |
+    if [[ $TRAVIS_PHP_VERSION != "nightly" ]]; then
+      travis_wait composer install --no-interaction --no-progress --no-scripts --no-suggest --optimize-autoloader --prefer-dist --verbose
+    else
+      composer require --no-update --no-suggest --no-scripts phpcompatibility/php-compatibility
+      travis_wait composer install --no-dev --no-interaction --no-progress --no-scripts --no-suggest --optimize-autoloader --prefer-dist --verbose --ignore-platform-reqs
+    fi
   - |
     if [[ ${PHPCS_VERSION:0:3} < "2.2" ]]; then
       # Rename the PHPCompatibility directory as PHPCompatibility 7.x wasn't fully compatible with Composer yet.

composer.json

@@ -23,9 +23,9 @@
     "source": "https://github.com/dealerdirect/phpcodesniffer-composer-installer"
   },
   "require": {
-    "php": "^5.3|^7",
+    "php": ">=5.3",
     "composer-plugin-api": "^1.0",
-    "squizlabs/php_codesniffer": "^2|^3"
+    "squizlabs/php_codesniffer": "^2 || ^3"
   },
   "require-dev": {
     "composer/composer": "*",