Ouch. How long does manual testing take? With unit tests, after a change I can test all code paths with various inputs/outputs in seconds.
How do you do that manually? Load the page in the browser and see if it works? What if it’s a complex page that does something bashed on a large form? Do you fill out the entire form (for each possible error condition) each time? That seems like a very poor way of working both in terms of time spent and the quality of the testing.
I’d highly recommend giving TDD a try as it will improve both your code and your efficiency as a developer.