For me, just outputting variables only works when I know a method should be broken.
I use Xdebug in PHP Storm (available on other IDE's and editors as well)
It allows me to use line breaks and fully inspect anything that's set and how their values are changed and allows me to call single method even at (paused) runtime to see what behaviour the method really gives at any given point, which gives me a much better insight on how my code works and how to get it to work like it should.
I wholeheartedly recomend anyone to try a fuller-fledged debugger like that!
