In a post to his site Tomas Votruba takes a look at the "rocket science" behind the migration of DocBlocks to typehints in your PHP application.

What if you could add scalar typehints int, bool, string, null to all parameter type and return type by running a CLI command? But also all classes, parent, self and $this?

Do you think it's an easy task to move @param int $number to (int $number)?

He talks about some of the current tools that handle the conversion of type-hints to type checks, but points out that some of them break the code (as they don't have the right context). He shares the results of some of his own research using these tools and issues that can come up with code changes. He also includes issues that could come up with the use of self/parent and namespacing. The post ends with some instructions on using the rector/rector package to handle this refactoring in a bit better way (including the configuration required).