How to merge nginx php-fpm containers in kubernetes?

Question

PHP

Good afternoon. I'm trying to merge two containers in a pod.

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    app: app
  name: app-nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: app
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: app
    spec:
      volumes:
        - name: shared-files
          emptyDir: {}
        - name: shared-log
          hostPath:
            path: /env/var/log/nginx
        - name: nginx-config-default
          configMap:
            name: nginx-default
        - name: php-fpm
          configMap:
            name: php-fpm
        - name: php-fpm-xdebug
          configMap:
            name: php-fpm-xdebug
      containers:
        - image: nginx:1.15.9
          name: nginx
          ports:
          - containerPort: 80
          volumeMounts:
            - name: shared-files
              mountPath: /var/www/
            - name: shared-log
              mountPath: /var/log/nginx
            - name: nginx-config-default
              mountPath: /etc/nginx/conf.d/default.conf
              subPath: default.conf
        - image: app
          imagePullPolicy: Never
          name: app
          ports:
          - containerPort: 11080
          volumeMounts:
            - name: shared-files
              mountPath: /var/www
            - name: php-fpm
              mountPath: /etc/php/7.1/fpm/pool.d/www.conf
              subPath: www.conf
            - name: php-fpm-xdebug
              mountPath: /usr/local/etc/php/conf.d/xdebug-dev.ini
              subPath: xdebug-dev.ini
          lifecycle:
            postStart:
              exec:
                command: ["/bin/sh", "-c", "cp -r /app/. /var/www"]
status: {}

Why is the var/www folder in the pod empty even though there are files in the app container in the folder