For classes it's enforced since PHP 5. For scalars you get to chose between enforcement or type coercion for callers on a per-file basis.
However, as with other dynamically typed and interpreted languages, all of this is happening at run-time, so one of the biggest benefits of strong typing (type checking at compile time) doesn't apply.
However, as with other dynamically typed and interpreted languages, all of this is happening at run-time, so one of the biggest benefits of strong typing (type checking at compile time) doesn't apply.