In his latest post Larry Garfield talks about the Composer problem that was recently brought up by the Gentoo linux project and is related to how Composer packages and system-level shared libraries differ.
This is not a new complaint; Other distributions have complained about Composer's impact before. But fundamentally I think the issue stems from having the wrong mental model of how modern PHP works when viewed from a distribution or sysadmin perspective.
In a recent heated GitHub thread, several people referred to PHP "linking" to 3rd party libraries, as if they were shared C libraries. That is simply not the case. Neither "static linking" nor "dynamic linking" really applies to PHP. From a sysadmin perspective, PHP is closer to highly complicated bash scripts than anything else.
Larry starts with a bit of history on the subject, pointing out the two methods most developers used PHP code: copy/pasted from the web or installed via PEAR. He talks about the common issues with both approaches. He then talks about how modern PHP development and Composer related and how, from a sysadmin perspective, Composer is the "compile" step of PHP and only supports static links. He also makes some suggestions to the distribution packagers around how to handle these system-level Composer dependencies (and how to treat it like a "binary" if needed).
The mistake here is trying to treat dependent packages of modern PHP applications like shared libraries. They're not. The community has spoken, and PHP simply doesn't work that way anymore. Fighting that is a losing battle. But by viewing composer as a compiler, distributions can still slot PHP into their typical workflows and get all of the security update ease that they're looking for.