It should be a given that you test your changes before committing. I know sometimes we all get a bit lazy and figure short little fixes can't mess anything up. I am guilty of that as well. But we really should try to test it offline. If you aren't capable of setting up a php.net mirror, you really shouldn't be messing with this code.
I was also guilty of not having a local mirror for a long time, but now I have one, and I am testing every major commit before adding it. The minor commits go though "php -l" if I don't forget them...
Goba