When to use native assert in PHP

My team and I were having a discussion about unit tests, tests in general and runtime tests using assert();.

In my opinion, assert()s are powerful indicators when used with a good error/exception handler and project-wide error levels - in combination with realtime analysis using Kibana for example.

My colleagues argued that there is no use-case for assert(), at least in PHP 5 (because further functionality was added in PHP 7 only).

My question is, when is it technically useful to implement assert()? I am explicitly asking for a technical advantage, not a personal opinion.