In a post in the Laravel News site, they quickly cover one of the many changes coming with the next jump in versions of the PHP language (v7.3): trailing commas in function calls.

Well PHP 7.3 won’t have arrow functions (that would be dreamy). However, trailing commas in function calls is an excellent addition coming to PHP 7.3.

In PHP 7.3, trailing commas in function calls will be valid syntax. That is to say, you can use trailing commas when calling functions, but not defining them.

They then include two places where these trailing commas could be useful: in the use of variadic functions and in PHP array definitions. The remainder of the post shows the concept of "trailing commas" in other languages including Javascript, Python, and Haskell. The first alpha release of PHP 7.3 has been released if you'd like to try this out with your own code.