Common Problems & Solutions for Working with Composer

If you have been using Composer for a while now, you have probably encountered some strange problems now and again. Sometimes, Composer will fail to install or update some project, and gives only a long, cryptic list of projects and versions that it claims are in conflict, with an unhelpful recommendation to not install some project that you need. Other times, a project might install fine, but not work right--even though the same code was running perfectly on another computer just recently. A collection of workarounds are often used to address these problems. Deleting the lock file and vendor directory. Installing things in a different order. Running `composer update some/project --with-dependencies`. Trying something like this can get your project working again, but why is Composer behaving this way? In this brief session, we will examine the implications of what being a per-project dependency manager means for Composer, and how using it consistently with its intended use patterns can help avoid these problems in the first place.