This is not terribly important, but I want to find out if you can possibly have HTMLPurifier omit the double quotes around arguments. When it filters HTML it usually reformats it into XHTML syntax.
But I would prefer <div class=alphanum> rather than class="xyz" in the output - whenever possible.
The config settings http://htmlpurifier.org/live/configdoc/plain.html provide no obvious option, and I didn't bother to look through the code (500K do scare you away). HTMLPurifier does use DOMDocument at some point. I'm not sure if this is just for pre-parsing, or if it's for output serialization (then I could answer the question myself with: No).
I've glanced through the htmlpurifier tag, found nothing. And enabling the experimental(?) HTMLPurifier/Lexer/PH5P.php parser doesn't change the output behaviour.
So is there an uncommon setting or tweak for that?
HTML Purifier specifically quotes all of its attributes for security reasons. There is no knob to turn it off.