Running complex tasks in Phing can mean running out of memory, especially when altering or changing lots of files. I was recently working on a image sorting Phing project that sorted images based on EXIF information.
Phing has a few different tasks and elements that allow you to select paths of code execution depending on what you need to happen in a build file. These are limited to loops and if statements, but a lot of functionality can be covered with just a couple of lines of XML.
The other day I was experimenting with Git hooks. These are scripts that you can execute before certain actions are run in Git. For example, you might want to ensure that forced updates are not run, ensuring respository files have the correct permissions after merging, or that the files have ASCII standard names before being committed.
I use Phing for a lot of different tasks, it helps me to automate things that I would otherwise mess up if left to my own devices. Prime candidates for Phing scripts are things that I don't do that much and forget how to do them, or that have a number of complex steps.
Running a simple syntax check over your files is a good way to save time. This can be when testing code but best practice is to not to even commit code that contains syntax errors.