Changed Semantics

When it comes to migrating existing code to PHP 7, backward incompatible changes to the language present the biggest challenge to application developers. It goes without saying that the PHP core developers try to avoid these types of changes at all costs. Sometimes, however, changes to PHP’s behaviour will be necessary. Luckily, in most cases, only more or less obscure edge cases will be affected. Nevertheless, you should take the time and work through your codebase, making adjustments where necessary. Determining whether a certain piece of code will be affected can be tricky, however, especially if you do not have enough test automation.