Shared experience: failed ton install flarum with docker and caddy

Melfos-md

Hi everyone,

After spending two full days trying to get Flarum up and running using Docker setup (PHP-FPM + Caddy), I wanted to share my experience. I am not an IT professional and I don't know anything about php.

I just share what I understood about it for others.

### Initial setup
I used this Dockerfile

FROM php:8.3-fpm
RUN apt-get update && apt-get install -y \
    curl \
    git \
    unzip \
    libzip-dev \
    libpng-dev \
    libjpeg-dev \
    libfreetype6-dev \
    && docker-php-ext-configure gd --with-freetype --with-jpeg \
    && docker-php-ext-install zip pdo pdo_mysql gd \
    && curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer

WORKDIR /var/www/html

because gd is required.
I set up a docker compose with mariadb and connected it on the network of my pre-existing caddy docker.
I used the Caddyfile from documentation and installed flarum with composer inside the docker instance.

Installation fails on PHP 8.3 with flarum/flarum:¹.8.0 due to deprecated string syntax

PHP Deprecated:  Using ${var} in strings is deprecated, use {$var} instead
in /var/www/html/vendor/flarum/core/migrations/2022_05_20_000000_add_timestamps_to_groups_table.php on line 23
...
PHP Fatal error:  Uncaught Laminas\HttpHandlerRunner\Exception\EmitterException:
Unable to emit response; headers already sent

As a result:

The database was populated
No config.php is created
On reload, the installer reappeared.

I solved this by downgrading FROM php:8.3-fpm to FROM php:8.1-fpm

Caddy

I also had trouble with Caddy

monurl.org {
    root * /var/www/html/public
    php_fastcgi flarum_php:9000

    header /assets/* {
        +Cache-Control "public, must-revalidate, proxy-revalidate"
        +Cache-Control "max-age=25000"
        Pragma "public"
    }

    file_server
}

If I understand well, flarum is a kind of SPA so I tried this and even if caddy php_fastcgi directive is supposed to handle that I tried :

rewrite * /index.php

allowing to access the install form by accessing / ; but after the install I got 404 http codes.

Then:

try_files {path} {path}/ /index.php

But even with that, Caddy served 404s for real files like /index.php and /assets/forum.css until I verified that the root path matched the real mount in the container, and that the files actually existed.

Now, I just give up.

I hope this post saves someone else hours of frustration 🙏
Happy to provide more details if needed.

Cheers,
Romain