The problem was that I was using the plain PHP image directly, and the mysqli extension was not included inside the PHP container. To fix this, we need to install the mysqli extension. There are two ways to do this:

1, Manually Install mysqli in the Running Container

• Start the PHP container.

• Access the container’s CLI:

  docker exec -it <php-container> bash

• Install the mysqli extension using:

  docker-php-ext-install mysqli

• Restart the container to apply the changes.

• Note: This method is temporary, and the changes will be lost if the container is rebuilt.

2, Build a Custom Docker Image with mysqli Pre-installed

• Create a custom Docker image that automatically installs and enables the mysqli extension.

• This ensures that the extension is always available, and no manual installation is needed each time the container is run.

I ended up going with the second approach, creating a custom Docker image, which solved the problem and ensured everything works smoothly.

Thanks to everyone!!