switch from docker-php scripts to apk add

Dockerfile

@@ -7,8 +7,25 @@ ENV WEBSERVER_PORT=8080
 
 COPY start-container.sh /usr/local/bin/start-container
 
-RUN apk add --no-cache curl-dev libxml2-dev oniguruma-dev composer npm \
-    && docker-php-ext-install ctype curl dom fileinfo filter mbstring pdo session xml \
+RUN apk add --no-cache \
+        curl-dev \
+        libxml2-dev \
+        oniguruma-dev \
+        libpng-dev \
+        icu-dev \
+        php-ctype \
+        php-curl \
+        php-dom \
+        php-fileinfo \
+        php-filter \
+        php-mbstring \
+        php-session \
+        php-xml \
+        php-intl \
+        php-bcmath \
+        php-pdo_mysql \
+        composer \
+        npm \
     && chmod +x /usr/local/bin/start-container
 
 EXPOSE ${WEBSERVER_PORT}