Backward Incompatible¶

A feature is backward incompatible when it cannot work with a previous version, and requires a specific version, or more recent.

For example, the function str_contains is backward incompatible, as it was introduced in PHP 8.0, and is not available in previous versions.

The keyword throw can be used in expressions such as check() or throw new Exception since PHP 8.0. In older versions, throw was available, but needed to be an instruction on its own.