Is it possible to replace (monkeypatch) PHP functions?

Question

You can do this in Python, but is it possible in PHP?

>>> def a(): print 1
... 
>>> def a(): print 2
... 
>>> a()
2

Answer 1

The accepted answer is excellent!!! I will just add,that you can put your codes in Namespace brackets and then the default GLOBAL-SPACE is resetted.

some other ways:

1) rename_function($old_name,$new_name)

2) override_function($old_name, $parameters, $new_func)

and rarely used:

3) runkit_function_rename(...)

4) runkit_function_redefine(...)