What is PHP syntax highlighting?

Apologies if this has been asked thousands of times before, but I couldn’t find it in the FAQs, and I can’t search for it as the search function only allows 4+ character searches.

Thanx.

I’m guessing you read about this on the vBcode page?
It’s a special vB code option to highlight syntax keywords for the PHP programming language. Why PHP only, and not other programming languages like Ada, Pascal, Fortran, C, C++, Java, etc…? Because vBulletin (the software product) is written in PHP.
You can read more about that scripting language here.