There was a time, back when I was working with PHP 5, when I found the Standard PHP Library (SPL) an extremely powerful and useful toolbox; and I particularly enjoyed working with SPL’s Iterators and Datastructures. Sadly, SPL was always a somewhat forgotten component of PHP, even when it was incorporated into core, probably due to the lack of documentation (although Pete Cowburn and the other PHP documentors did work hard to improve it over the years). With the arrival of PHP 7, SPL seems to have dropped even further into a backwater: generally we create our own exception classes, though we may sometimes use those in the SPL; we rely on Composer to handle autoloading, rather than using SPL directly to set up our autoloading manually; and Datastructures (one of my favourite SPL components) are better implemented in Rudi Theunissen’s ext-ds library.
But although much of the SPL is now outdated, or has been superseded by better language elements; some components are still useful. SPL’s Iterators are confusingly named, and there’s little in the documentation that explains when and how they can/should be used, but if you can learn to understand them, they are still powerful tools even with PHP 7; especially as they work with any Traversable (like Iterators and Generators, or the Collection objects provided by many frameworks), not simply with arrays.
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