With jwilder nginx-proxy, how to proxypass a subdirectory url to a specific container?

I use jwilder/nginx-proxy to make a reverse proxy. I try to redirect http://localhost:8000/api to a specific php service.

The directory structure:

.
+-- docker-compose.yml
+-- nginx
+-- nodejs
|   +-- index.js
|   +-- …
+-- php
|   +-- api

docker-compose.yml:

version: "3.1"

services:

  nginx-proxy:
    image: jwilder/nginx-proxy:alpine
    ports:
      - "8000:80"
    volumes:
      - ./php:/srv/www
      - /var/run/docker.sock:/tmp/docker.sock:ro

  nodejs:
    image: node:alpine
    environment: 
      - NODE_ENV=production
      - VIRTUAL_HOST=localhost
      - VIRTUAL_PORT=8080
    expose:
      - "8080"
    working_dir: /home/app
    restart: always
    volumes:
      - ./nodejs:/home/app
    command: ["node", "index.js"]

  php:
    image: php:apache
    environment:
      - VIRTUAL_HOST=localhost
    volumes:
      - ./php:/var/www/html

This works fine for the nodejs service.

Now, I would like to redirect calls to http://localhost:8000/api to the php service. I imagine that I have to add to the nginx conf something like:

server {
  location /api {
    proxy_pass http://php:80/api;
    proxy_set_header Host $host;
  }
}

This feature is not built into the lib. So, how can I achieve that?