Add PHP 8 support

Author: eldarQa

.gitignore

@@ -2,3 +2,4 @@
 /composer.phar
 /vendor/
 /phpunit.xml
+.phpunit.result.cache

.travis.yml

@@ -7,11 +7,11 @@ cache:
     - "$HOME/.composer/cache"
 
 php:
-  - 7.0
-  - 7.1
+  - 8.0
   - nightly
   - hhvm
 
+
 matrix:
   allow_failures:
     - php: nightly
@@ -30,7 +30,7 @@ install:
 
 script:
   - composer check-code
-  - if [ "$TRAVIS_PHP_VERSION" == "7.1" ]; then composer test-cov; else composer test; fi
+  - if [ "$TRAVIS_PHP_VERSION" == "8.0" ]; then composer test-cov; else composer test; fi
 
 after_script:
-  - if [ "$TRAVIS_PHP_VERSION" == "7.1" ]; then composer test-cov-upload; fi
+  - if [ "$TRAVIS_PHP_VERSION" == "8.0" ]; then composer test-cov-upload; fi

composer.json

@@ -24,11 +24,11 @@
         }
     ],
     "require": {
-        "php": "^7.0"
+        "php": "^8.0"
     },
     "require-dev": {
         "jakub-onderka/php-parallel-lint": "^0.9.2",
-        "phpunit/phpunit": "^6.3",
+        "phpunit/phpunit": "^9.3.8",
         "squizlabs/php_codesniffer": "^3.0"
     },
     "autoload": {