You fix the bug, next day you have to fix that bug again, and a week after you're fixing it once more. Sound familiar? If yes, it's probably because you're not using automated tests. Hey, you will have to test in either case, so make your life easier and make it automatic. Not only will you know right away if you broke something, but at the same time it will help you to write better code.
You're always testing, the only difference is if it's manual or automatic.
Don't worry if you have no idea to start with automated testing. Together with KnpUniversity we made a course which will show you everything, teach some of theory, and will make you laugh a time or two.
Go to the KnpUniversity and learn how to test your code with PHPUnit.