PHP isn't a lang. to edit via WYSIWYG... you'd need to emulate a server + php mod and that... thats just a weird thought.
I like ginf for HTML WYSIWYG but it's not mature enough to win me over 100%. I like Dream weaver
even tho it's not GPL.. it helps me get one step closer is creating GPL'd software/service
(ginf has poor support for tables IMO)
Mozilla has a decent composer to but im sure you already know that.