The vast majority of people using a package manager in the PHP ecosystem are using composer. It makes sense to call it "the" package manager.
Personally, I wouldn't... I worked with pear and pecl and composer is just far more pleasant to interact with.
Installing libraries globally is inconvenient for developers. Sadly, most Linux package managers have same problem and do not allow you to install several versions of PHP or Node.
PEAR is an abandoned tool used by no one. Arguing for it to be considered "the" package manager is a really weird fight to pick.