Merge pull request #193 from digitalist-se/master

Just some suggestion to maybe improve some documentation

docs/install-agent.md

+# Install SkyWalking PHP Agent
+
+## Requirements
 When building directly from Git sources or after custom modifications you might also need:
 * php 7+
 * golang 1.13
 * SkyWalking Collector
 
+## PHP extension + Agent
+The collect data from your instance you need both the PHP extension, and the agent. 
+No pre built binaries or PHP extension are availble at the moment, so you need to
+build them from source.
 
-# Install SkyWalking PHP Agent
-
-You can run the following command to install the SkyWalking PHP Agent in your computer.
+You can run the following commands to install the SkyWalking PHP Agent.
 
 ## Install PHP Extension
 ```shell script
@@ -15,11 +20,10 @@ cd SkyAPM-php-sdk
 phpize && ./configure && make && make install
 ```
 
-## Install sky-php-agent (download or build)
-### Download sky-php-agent
-Go to [release](https://github.com/SkyAPM/SkyAPM-php-sdk/releases) page to download the sky-php-agent required by your platform. Currently there are Linux (amd64, arm64) and Mac versions.
-
+## Install sky-php-agent
 ### Build
+For installing the sky-php-agent, you first need to build it:
+
 ```shell script
 cd SkyAPM-php-sdk
 go build -o sky-php-agent agent/cmd/main.go
@@ -52,4 +56,24 @@ skywalking.app_code = MyProjectName
 sky-php-agent --grpc 127.0.0.1:11800
 ```
 
-### ⚠️⚠️⚠️ Warning *Make sure PHP has read and write permissions on the socks file*
\ No newline at end of file
+### ⚠️⚠️⚠️ Warning *Make sure PHP has read and write permissions on the socks file*
+
+## Dockerfile
+
+### Multi stage build example (starting point)
+```bash
+FROM golang:1.13 AS builder
+ARG SKY_AGENT_VERSION=3.2.6
+WORKDIR /go/src/app
+RUN wget https://github.com/SkyAPM/SkyAPM-php-sdk/archive/${SKY_AGENT_VERSION}.tar.gz; \
+    tar xvf ${SKY_AGENT_VERSION}.tar.gz
+RUN mv SkyAPM-php-sdk-${SKY_AGENT_VERSION} build
+RUN cd build; \
+    GOOS=linux GOARCH=amd64 go build -o sky-php-agent-linux-x64 ./agent/cmd/main.go
+
+FROM php:7.2.28-fpm-alpine3.11
+# Copy from builder
+COPY --from=builder /go/src/app/build/sky-php-agent-linux-x64 /usr/local/bin/sky-php-agent
+RUN apk update && apk upgrade && apk add --no-cache autoconf libc6-compat libcurl curl-dev icu-dev & \
+    apk add --no-cache --virtual .build-deps $PHPIZE_DEPS
+```