GlobalMock allows you to test and refactor code that calls global functions that have side effects by simulating their behavior without actually running them.
It can be very difficult to test and therefore refactor PHP that uses global functions that rely on side-effects. For example, if your application calls mysql_query it can be hard to refactor and test the code without resetting the state of the database before running the test each time. Many languages allow you to redifine functions, so writing mock object libraries is easy. Unfortunately PHP expressly forbids redefining functions. There are some solutions but they require 3rd party modules and are self-admitted hacks.
Before running global functions run $gm = GlobalMock::getInstance();. Then prepend all calls to global functions
with $gm->function_name(). You can see an example of an original program
and a testable version in the example folder.