Wouldn't you consider spl_autoload_register an interoperability solution? Only your defined autoloading function would then need to know how your file system is structured, there'd be no need for include_path declarations and you wouldn't have to explicitly declare paths for each class.
But that's besides the point. I just want to emphasize the point that
performance should not be a criteria for justifying it going into the
core...There also seems to be the perception among some php devs that autoloading
is now the preferred way of loading PHP code.So adding require() or other explicit dependencies add the top of your
scripts is no longer the appropriate way to do things.SplClassLoader solves an interoperability problem. Shouldn't it be promoted
as such?So overall I agree with Anthony, performance shouldn't even be an argument.
If you want to solve a "code loading problem", autoloading everything is far
from a silver bullet and in my opinion not a good solution.The main question seems to be: does interoperability belong in core?