Upgrade PHP version in docker-compose to 7.2 (#238)

Author: Gildus

docker-compose.yml

@@ -1,9 +1,9 @@
 version: '2'
 services:
   php:
-    image: yiisoftware/yii2-php:7.1-apache
+    image: yiisoftware/yii2-php:7.2-apache
     volumes:
       - ~/.composer-docker/cache:/root/.composer/cache:delegated
       - ./:/app:delegated
     ports:
-      - '8000:80'
+      - '8000:80'