How important is Unit Testing taken by employers, is it something that every developer should have as one of their skills, do some jobs require it more than others or is a simple test like handing out a piece of software to be used by friends family etc sufficient enough.

Given that Unit Testing, or some equivalent testing method, is the only way to locate errors in the untyped PHP language I would assume serious employers would consider it a necessary skill.

@Full Spectrum
Its not an untyped language it is a loosely typed language. You can cast values to a particular type and do type comparisons if you want/need too.

Unit testing is a very powerful mechanism for development, but in my experience it is a different mindset than just sitting down and writing code. Generally you see unit testing talked about with TDD (Test Driven Development). In other words, you design your functionality, write a failing test, write code to pass the test and finally refactor the code to a certain standard level.

Unit testing really shines when you have a system that is heavily tested and then you are tasked with making changes to already existing classes/functions throughout the existing system. Because your tests all pass to start, you write new failing tests and then implement the code necessary to pass those tests. As long as your original tests still pass and your new tests pass, then you have added your additional functionality without breaking any existing code.

Where as without testing, its next to impossible to know for sure that everywhere that piece of code is used is still functional until a bug or issue is found.

Just my $0.02 hope it helps.