Add redis; use alpine images

docker/php/Dockerfile

@@ -1,7 +1,8 @@
-FROM php:7.3-fpm
+FROM php:7.3-fpm-alpine
 
-RUN apt-get update
-RUN apt-get install -y libgmp-dev
+#RUN apt-get update
+#RUN apt-get install -y libgmp-dev
+RUN apk add gmp-dev
 
 # Copy any config files in
 COPY ext-opcache.ini $PHP_INI_DIR/conf.d/
@@ -9,8 +10,6 @@ COPY ext-opcache.ini $PHP_INI_DIR/conf.d/
 RUN ln -sf /dev/stderr /var/log/fpm-error.log
 
 RUN docker-php-ext-install \
-  mysqli \
-  pdo \
   pdo_mysql \
   gmp \
   opcache