Add PHP 7.4 support to testing suite

Author: mmeyer2k

.circleci/config.yml

@@ -62,6 +62,22 @@ jobs:
           key: source-php7.3-{{ .Branch }}-{{ .Revision }}
           paths:
             - vendor
+  php-74:
+    docker:
+      - image: circleci/php:7.4
+    steps:
+      - checkout
+      - restore_cache:
+          keys:
+            - source-php7.4-{{ .Branch }}-{{ .Revision }}
+            - source-php7.4-{{ .Branch }}-
+            - source-php7.4-
+      - run: composer require phpunit/phpunit
+      - run: php vendor/phpunit/phpunit/phpunit
+      - save_cache:
+          key: source-php7.4-{{ .Branch }}-{{ .Revision }}
+          paths:
+            - vendor
 
 workflows:
   version: 2
@@ -70,3 +86,4 @@ workflows:
       - php-71
       - php-72
       - php-73
+      - php-74