I have created a new account just for this damn problem.
I have created a local web server in my raspberry, using Docker i created a composer with phpmyadmin, mariadb, php 8.2
Everything was working perfectly but then the db connector mysqli did not work:

I get always this message:

Fatal error: Uncaught Error: Class “mysqli” not found in /var/www/html/Example/loginConfirmation.php:10 Stack trace: #0 {main} thrown in /var/www/html/Example/loginConfirmation.php on line 10

the docker-compose.yml:

version: '3.1'

services:
  web:
    image: php:8.2-apache
    ports:
      - "80:80"
    depends_on:
      - db
    volumes:
      - ./html:/var/www/html/
    container_name: web

  db:
    image: mariadb:10.6
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: prova1
      MYSQL_DATABASE: db_utenti
      MYSQL_USER: root

  phpmyadmin:
    image: phpmyadmin
    restart: always
    ports:
      - "8080:80"
    environment:
      - PMA_ARBITRARY=1

and the dockerfile:

FROM php:8.2-apache

RUN docker-php-ext-install mysqli

COPY ./html /var/www/html/

RUN a2enmod rewrite

RUN chown -R www-data:www-data /var/www/html

something to understand:

-I am really new to Docker so you should not omit anything (I could have failed trivial things)
-I tried to install mysqli even in a non-docker enviroment with apt-get install mysqli but it still didnt work.

Thanks a lot to everyone!

I tried with different types of composer and dockerfile, I also tried searching for my problem but everything I’ve found online didnt work, I even used chatgpt to help me with this but nothing it only made me troubles.