Get docker container ip

container_ip.bash

#!/usr/bin/env bash
#inside docker container
HOST_IP=$(/sbin/ip route|awk '/default/ { print $3 }')
CONTAINER_IP=$(curl "$HOST_IP:8000" 2>/dev/null)
echo "container ip is $CONTAINER_IP"

host.sh

#!/usr/bin/env bash
#then run something like this inside ./host
php -S 0.0.0.0:8000

index.php

#!/bin/env php
# ./host/index.php on host
echo $_SERVER['REMOTE_ADDR'];