In a previous post, Docker PHP/PHP-FPM Configuration via Environment Variables, I described how to use environment variables to configure PHP FPM and CLI. With my method you can override one of over 650 PHP INI settings. More INI settings are but a PR away!

In a more recent post, PHP Modules Toggled via Environment Variables I extended this concept to include modules. You can now easily (and quickly!) enable over 20 common modules, including GD, Imagick, Mongodb, and more! The images I built come with over 30 modules installed, with a small selection enabled by default, and the rest toggable by simple environment variables.

With these two concepts combined my other post, Developing at Full Speed with Xdebug becomes that much more powerful, because now you can easily enable Xdebug via a very simple env var flag. A truly delay-free debug-ready development environment has never been easier to maintain.

However, my Xdebug post uses a method that requires two separate PHP-FPM servers, one with Xdebug enabled and another without. To run a normal PHP project you would be required to run 4 containers in total:

2 PHP (FPM)

1 Nginx (Webserver)

1 MySQL (Database)

While this falls inline with Docker’s vision of one-container per responsibility, it is a hassle to have to maintain separate containers for both Nginx and PHP, with the main reason being that both separate services need access to your project’s source code in order to properly work.

You can argue that PHP-FPM depends on a webserver to actually function and this responsibility can be considered as one. Thus, one container running both Nginx (or your webserver of choice) and PHP is desirable.

Managing Multiple Services Under Docker

Docker containers can run multiple services just fine. However, the daemon actively checks only a single main process which includes monitoring it for health (is this service still running?) and using it for stdout/stderr logging.

The official Docker documentation recommends using either writing your own wrapper script, or using a process manager like supervisord .

You could install Supervisord. It is a great process manager! However, why go that route when you can use a Docker-ready image to build from?

Enter baseimage-docker.

This Ubuntu 18.04-based image comes preinstalled and configured with nifty tools like runit for process management (Does not require crazy weird init.d config files!), syslog-ng for log management, and cron which is sorely-missing from most Docker images!

I will not go into detail about baseimage-docker as their documentation is top-notch. Later you will be able to see what I created using this tool as an example.

Setting up Nginx

The Nginx images extend my PHP images. We already have a strong PHP-focused base to start from and can simply add Nginx to it.

The runit file is fairly simple.

In it we spin up Nginx as most folks do: nginx -g "daemon off;"

However, the Nginx build I am using comes with support for the handy Perl module. This allows us to pass environment variables to the Nginx config files. Normally Nginx has no support for this (which is a huge gaping hole, in my opinion) but using the Perl module you get a workable implementation.

The one thing I have baked in to the Nginx images is passing in an Xdebug port.

This works nicely with my Developing at Full Speed with Xdebug blog post.

You can setup Nginx env var as follows:

perl_set $phpfpm_xdebug_port 'sub { return $ENV{"PHPFPM_XDEBUG_PORT"}; }' ;

The runit file then looks like this:

PHPFPM_XDEBUG = ${ PHPFPM_XDEBUG :- "" } if [ " ${ PHPFPM_XDEBUG ,, } " = "on" ] ; then PHPFPM_XDEBUG_PORT = 9999 else PHPFPM_XDEBUG_PORT = 9000 fi exec nginx -g "daemon off; env PHPFPM_XDEBUG_PORT= ${ PHPFPM_XDEBUG_PORT } ;"

Everything hinges on the PHPFPM_XDEBUG env var. If it is set to On or on Nginx is told to use port 9999 for Xdebug requests, otherwise to use the standard 9000 .

The final piece of the Nginx puzzle is the virtual host config:

map $cookie_XDEBUG_SESSION $my_fastcgi_pass { default 127 .0.0.1:9000 ; xdebug 127 .0.0.1: ${ phpfpm_xdebug_port } ; }

If Nginx detects a cookie named XDEBUG_SESSION it uses ${phpfpm_xdebug_port} , otherwise defaults to the standard 9000 .

What happens when Xdebug support is not requested is that both cases would be interpreted as simply

map $cookie_XDEBUG_SESSION $my_fastcgi_pass { default 127 .0.0.1:9000 ; xdebug 127 .0.0.1:9000 ; }

This allows us to toggle Xdebug without having to actually make any file changes.

Likewise, if Xdebug support is enabled (via the PHPFPM_XDEBUG=On env var) then it would be interpreted as

map $cookie_XDEBUG_SESSION $my_fastcgi_pass { default 127 .0.0.1:9000 ; xdebug 127 .0.0.1:9999 ; }

Setting up PHP-FPM

The PHP-FPM runit init file is already created at the jtreminio/php:7.2 level. Nginx can immediately start working with this existing service and nothing else is required on your part. However, we want to also optionally add a second PHP-FPM instance with Xdebug enabled but only when PHPFPM_XDEBUG=On !

runit requires a bash file with +x flag set (making it executable). One route we could have taken was to simply mount a file volume via a docker-compose.yml file but unfortunately any files shared in this manner are not set as executable. This means we have to bake in the init file into the image itself. However, if we want to continue down the path of not requiring any file system changes and make everything configurable via env vars then we need to figure out a way to prevent runit from running a second PHP-FPM instance when Xdebug is not to be enabled.

The solution I implemented does just that.

If PHPFPM_XDEBUG is not set to On|on then a harmless, low-resource service is run:

exec tail -f /var/log/fpm-xdebug-tail

This is because runit needs to run something, and simply exiting at this point would cause the daemon to try restarting the service over and over. There is no disable flag to tell runit, “Hey, don’t run this!”.

Otherwise, if PHPFPM_XDEBUG=On then a second PHP-FPM service is run using

exec /usr/sbin/php-fpm \ -d FPM.pid = "/var/run/php-fpm/php-fpm-xdebug.pid" \ -d FPM.listen = "127.0.0.1:9999" \ [ ... ]

We override the pid and listen directives to prevent any collisions with the non-Xdebug PHP-FPM instance.

Bonus: Setting up Apache

Since we are using PHP-FPM the webserver engine becomes much easier to switch out. As long as it can speak TCP it is ok, which means adding Apache support is fairly simple.

The Dockerfile for the Apache image is very similar to the Nginx one.

Likewise, the runit init file for Apache looks similar and the runit init file for PHP-FPM is identical.

Apache has built-in support for env vars (looking at you, Nginx) so only the vhost config file needs changed.

Apache has no map directive, but does support If/Else :

<FilesMatch "\.php $ " > <If "%{HTTP_COOKIE} =~ /XDEBUG_SESSION/" > SetHandler proxy:fcgi://127.0.0.1: ${ PHPFPM_XDEBUG_PORT } </If> <Else> SetHandler proxy:fcgi://127.0.0.1:9000 </Else> </FilesMatch>

The same idea from Nginx applies here, $PHPFPM_XDEBUG_PORT defaults to 9000 unless PHPFPM_XDEBUG=On then it defaults to 9999 .

Try It Out

You can try this out fairly quickly, but first some helpers.

Grab the PhpStorm bookmarklets. You do not need to use PhpStorm to use these, they simply create an XDEBUG_SESSION cookie in your browser. This is the cookie the webserver listens for. Again, if this cookie does not exist all traffic is routed to the non-Xdebug PHP-FPM instance, and vice-versa.

Next, setup Traefik. You may remember Traefik from my Traefik on Docker for Web Developers post. It is an amazing tool that helps map domain names to containers.

TRAEFIK = $( docker container ls --filter name = traefik_proxy | grep -c traefik_proxy || true ) if [ ${ TRAEFIK } -eq 0 ] ; then NETWORK = $( docker network ls --filter name = traefik_webgateway | grep -c traefik_webgateway || true ) if [ ${ NETWORK } -eq 0 ] ; then docker network create --driver bridge traefik_webgateway fi docker container run -d \ --name traefik_proxy \ --network traefik_webgateway \ --publish 80 :80 \ --publish 8080 :8080 \ --restart always \ --volume /var/run/docker.sock:/var/run/docker.sock \ --volume /dev/null:/traefik.toml \ traefik --api --docker --docker.domain = docker.localhost --logLevel = DEBUG fi

We setup Traefik via bash instead of a docker-compose.yml file so it is not tied to a specific project (the container name would have the parent directory prepended to it otherwise).

Now you can run the PHP/Nginx instance using:

version : '3.2' networks : public : external : name : traefik_webgateway services : web : image : jtreminio/php-nginx : 7.2 labels : - traefik.backend=php-nginx - traefik.docker.network=traefik_webgateway - traefik.frontend.rule=Host : php-nginx.localhost - traefik.port= 8080 networks : - public volumes : - ./ : /var/www/ environment : - PHP.display_errors=On - PHP.error_reporting=- 1 - PHPFPM_XDEBUG=On

Run docker-compose up and then open php-nginx.localhost in Chrome (or another browser if you have dnsmasq installed).

Create an index.php file that simply contains <?php phpinfo(); to test this out.

If you want to try with Apache, use the following:

version : '3.2' networks : public : external : name : traefik_webgateway services : web : image : jtreminio/php-apache : 7.2 labels : - traefik.backend=php-apache - traefik.docker.network=traefik_webgateway - traefik.frontend.rule=Host : php-apache.localhost - traefik.port= 8080 networks : - public volumes : - ./ : /var/www/ environment : - PHP.display_errors=On - PHP.error_reporting=- 1 - PHPFPM_XDEBUG=On

Run docker-compose up and then open php-apache.localhost in Chrome (or another browser if you have dnsmasq installed).

You can try the Xdebug feature by either commenting out PHPFPM_XDEBUG=On or changing it to anything not On|on : PHPFPM_XDEBUG=Off .

Wrapping It Up

This project is the end result of weeks/months testing different solutions, always poking and refactoring while trying to achieve a truly immutable image.

Not to say that this project is done, but I believe it is on the right path to becoming something many developers and companies can build their Docker deployments on.

Not needing to manage separate containers for PHP/Nginx|Apache, enabling or disabling Xdebug and many other modules, and configuring PHP with nothing more than simple environment variables reduces complexity and speeds up development time.

I would love to hear your feedback on this and would be elated if you would drop me a line if you decide to implement my images into your workflow.

Until next time, this is Señor PHP Developer Juan Treminio wishing you adios!