For the most part, PHP 5.x code can run unchanged on PHP 7. There are a few changes, however, that are classified as backwards incompatible. What this means is that if your PHP 5 code is written in a certain way, or uses functions that have been removed, your code will break, and you'll have a nasty error on your hands.
The PHP 5 to PHP 7 Code Converter does two things:
WARNINGwhere changes in language usage have occurred, but where a re-write is not possible
Please note that after running the converter, your code is not guaranteed to work in PHP 7. You will still have ...