note 105474 deleted from book.spl by danbrown

Note Submitter: matthewkastor ---- There are many places in the manual where SPL documentation reads "this is undocumented" or "description here" ( note CachingIterator constants http://www.php.net/manual/en/class.cachingiterator.php ). This page helps explain some things, http://www.phpro.org/tutorials/Introduction-to-SPL.html but I don't know how accurate it is, when it was written, or if it's even all that good. I'm just not familiar enough with SPL to know. I'm leaving the link to phpro because there are things written on that page that seem to work, but aren't in the documentation here.