Let’s suppose you wanted to install the PDO extension. Here’s how.

Create your custom Dockerfile:

FROM php:8.2-fpm

RUN docker-php-ext-install pdo_mysql

The docker-php-ext-install command is provided by the official php image.

Build image

docker build php-with-pdo .

Test that extension was installed

docker run -it --rm my-php-image php -m | grep pdo_mysql

You should see pdo_mysql printed out in the console.