Hi,
recent changes in trunk require the SPL which is "available and compiled by default in PHP 5.0.x". However, compiled by default does not mean that each distro has compiled it (or that the sysadmin has installed the required package).
Starting with 5.3.0 this extension can no longer be disabled.
So, do we want to impose this dependency? I'm not sure but if yes, we should clearly state it in our doc and maybe add a warning about it in the code.
Marc