Unable to install extensions mbstring/openssl/pdo_mysql on php:8.1-fpm-alpine v.3.20

[kamyweb]

Unable to install extensions mbstring/openssl/pdo_mysql on php:8.1-fpm-alpine v.3.20

[jnoordsij]

Hey there!

Your problem is caused by the fact that you're accidentally mixing two PHP installation by using apk to install PHP extensions, as this will actually add an entire new PHP installation to the resulting image, rather than using the bundled one. To install additional extensions to this image, you could use the bundled docker-php-ext-install script. Given that mbstring and openssl are already part of the base image, something along the following lines should work:

FROM php:8.1-fpm-alpine

RUN apk add --no-cache <packages-you-need> && \
    docker-php-ext-install -j$(nproc) pdo_mysql && \
    php -m # smoketest

See also https://github.com/docker-library/docs/tree/master/php#how-to-install-more-php-extensions if you're looking for additional details.