Laravel API in Docker is returning HTML instead of JSON?

I'm dockerzing my Laravel API and going quite crazy.

Locally with either php artisan serve or symfony serve everything works well and has been working for years.

Now I'm finally dockerzing (not an expert in Docker) Laravel for production and having some problems.

The main one is that all the api routes return text/html as content type and not application/json, but locally it returns application/json.

The code base obviously is the same one. And the return of each api route is like this response()->json($data);

This is my dockerfile and it's being used in a docker-compose file. Anyone has any idea why?

It seems that all the laravel headers are being replaced, so it's probably a Docker problem rather than Laravel

FROM php:8.3-fpm-alpine3.20
 
RUN apk update && apk upgrade
 
# Essentials
RUN echo "Europe/London" > /etc/timezone
RUN apk add git zip unzip curl sqlite supervisor
 
# Install Python
RUN apk add python3 py3-pip
 
RUN apk add nodejs npm
RUN apk add nano
 
RUN apk add php83-gd \
    php83-imap \
    php83-redis \
    php83-cgi \
    php83-bcmath \
    php83-mysqli \
    php83-zlib \
    php83-curl \
    php83-zip \
    php83-mbstring \
    php83-iconv \
    gmp-dev
 
# dependencies required for running "phpize"
# these get automatically installed and removed by "docker-php-ext-*" (unless they're already installed)
ENV PHPIZE_DEPS \
    autoconf \
    dpkg-dev \
    dpkg \
    file \
    g++ \
    gcc \
    libc-dev \
    make \
    pkgconf \
    re2c \
    zlib \
    wget
 
# Install packages
RUN set -eux; \
    # Packages needed only for build
    apk add --virtual .build-deps \
    $PHPIZE_DEPS
 
RUN apk add --no-cache linux-headers
 
# Packages to install
RUN apk add  curl \
    gettext-dev \
    libmcrypt-dev \
    icu-dev \
    libpng \
    libpng-dev \
    libressl-dev \
    libtool \
    libxml2-dev \
    libzip-dev \
    libjpeg-turbo-dev \
    libwebp-dev \
    freetype-dev \
    oniguruma-dev \
    unzip 
 
# pecl PHP extensions
RUN pecl install \
    # imagick-3.4.4 \
    mongodb \
    redis
# Configure PHP extensions
RUN docker-php-ext-configure \
    # ref: https://github.com/docker-library/php/issues/920#issuecomment-562864296
    gd --enable-gd --with-freetype --with-jpeg --with-webp
# Install PHP extensions
RUN  docker-php-ext-install \
    bcmath \
    bz2 \
    exif \
    ftp \
    gettext \
    gd \
    # iconv \
    intl \
    gmp \
    mbstring \
    opcache \
    pdo \
    pdo_mysql \
    shmop \
    sockets \
    sysvmsg \
    sysvsem \
    sysvshm \
    zip \
    && \
    # Enable PHP extensions
    docker-php-ext-enable \
    # imagick \
    mongodb \
    redis \
    && \
    # Remove the build deps
    apk del .build-deps
RUN apk cache clean 
# fix work iconv library with alphine for PHP 8.1 broken
ENV LD_PRELOAD /usr/lib/preloadable_libiconv.so
# # Installing bash
# RUN apk add bash
# RUN sed -i 's/bin\/ash/bin\/bash/g' /etc/passwd
 
# Installing composer
RUN curl -sS https://getcomposer.org/installer -o composer-setup.php
RUN php composer-setup.php --install-dir=/usr/local/bin --filename=composer
RUN rm -rf composer-setup.php
 
# Configure supervisor
RUN mkdir -p /etc/supervisord/conf.d/
RUN touch /run/supervisord.sock
COPY ./docker-ops/backend/supervisord/laravel-worker.conf /etc/supervisord/conf.d/laravel-worker.conf
COPY ./docker-ops/backend/supervisord/supervisord.ini /etc/supervisord/supervisord.ini
 
# Cron Config
COPY ./docker-ops/backend/crontab /etc/crontabs/root
 
# Config PHP
COPY ./docker-ops/backend/php/local.ini /usr/local/etc/php/php.ini
# COPY ./ /var/www
COPY --chown=www-data:www-data ./my-app /var/www
COPY ./docker-ops/backend/scripts.env /var/www/resources/scripts/.env
COPY ./docker-ops/backend/.env.laravel /var/www/.env
 
 
# Install Python packages
ENV PIP_BREAK_SYSTEM_PACKAGES 1
RUN pip install -r /var/www/resources/scripts/requirements.txt
 
 
USER root
WORKDIR /var/www
 
EXPOSE 8000
 
CMD ["php", "artisan", "serve", "--host", "0.0.0.0", "--port=8000"]```