I used PHPDoc to document stuff, now there is native support to declare types. Then my IDE (Intelij) will highlight type related issues as errors or warnings. It will also show you lot of other errors like using the wrong parameter count, the wrong parameter types etc. With PHPDoc you can also document "magic" stuff like objects that are auto-generated from DB tables, so you get error checks and autocompletion on column names.

But I work on a small team.

We use PHPUnit for unit testing, but this is not related to types.