Using PIE in Docker
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:category:  PHP
:tags:      pecl, pie, docker
:date:      2025-10-09 20:51:00 +0300

As you may know, `PECL is now soft-deprecated and PIE is the recommended way to install exenetsions <rfc_>`__.

.. _rfc: https://wiki.php.net/rfc/adopt_pie_deprecate_pecl

The current PHP docker images do not package PIE executable.
Luckily there is `an instruction in the doc <doc_>`__ that says this:

.. _doc: https://github.com/php/pie/blob/main/docs/usage.md

.. code-block:: docker

    COPY --from=ghcr.io/php/pie:bin /pie /usr/bin/pie
    RUN pie install asgrim/example-pie-extension

It works but this solution is bad.
It will import a 6MB PIE executable as a dead weight.
Trying to find a solution to this solution, I stumbled on this blog post: rabbithole.wwwdotorg.org_.
Luckily ``RUN --mount`` can work with external images instead of stages and files instead of directories.
This allows us to collapse the installation into a single layer:

.. _rabbithole.wwwdotorg.org: https://rabbithole.wwwdotorg.org/2021/03/02/1-avoiding-docker-add-copy-layers.html

.. code-block:: docker

    RUN --mount=type=bind,from=ghcr.io/php/pie:bin,source=/pie,target=/usr/local/bin/pie \
        pie install asgrim/example-pie-extension

This will make your final image 6MB ligher.