Having PHP as my most useful skill.

I know various other languages, but they're either too exotic for professional use, or my knowledge about them doesn't have the same depth as with PHP.

People joke about how awful PHP is, and it's not entirely true. The incongruous stuff such as confusing parameter ordering can be fixed with libraries. And PHP7 fixed a lot of the ugly stuff. A good dev can certainly write structured, readable, performant PHP code.

But there is a real hard limit. PHP is missing more complex type definitions present in other languages. A weak type system is like building stuff with popsicle sticks and bits of duct tape, it works fast and perfectly fine for small projects, but the lack of strictness is a problem when you have thousands of classes intertwined in all kinds of complex factory, service and repository patterns. And the simple type hints are still newish and fully optional, which means a lot of people don't use them.

So I regret getting stuck in this self reinforcing loop, where I learn more about a very imperfect language through employment, and keep rolling into jobs using that skill because it's what I'm most experienced with.

ArgumentException(message, paramName)
ArgumentNullException(paramName, message)