Tony Marston writing about the proposed changed to PHP 7 that PHP 4 style constructors should be made invalid:
Millions of existing websites will not be able to upgrade to PHP 7 until their code is rewritten, and I fear this single BC break will make the move from PHP 5 to PHP 7 much slower than the move from PHP 4 to PHP 5.
I’m not sure this would require an actual rewrite and his bias really shows in the letter. However I have to agree that it will slow adoption even more.
Which side of the fence are you on? Implement a BC which might keep people from updating to more secure versions of PHP. Or don’t and have to support the old feature forever?