My answer will address the specific task of parsing Python in order to translate it to another language, and not the higher-level aspects which Ira addressed well in his answer.
In short: do not use the parser module, there's an easier way.
The ast module, available since Python 2.6 is much more suitable for your needs, since it gives you a ready-made AST to work with. I've written an article on this last year, but in short, use the parse method of ast to parse Python source code into an AST. The parser module will give you a parse tree, not an AST. Be wary of the difference.
Now, since Python's ASTs are quite detailed, given an AST the front-end job isn't terribly hard. I suppose you can have a simple prototype for some parts of the functionality ready quite quickly. However, getting to a complete solution will take more time, mainly because the semantics of the languages are different. A simple subset of the language (functions, basic types and so on) can be readily translated, but once you get into the more complex layers, you'll need heavy machinery to emulate one language's core in another. For example consider Python's generators and list comprehensions which don't exist in PHP (to my best knowledge, which is admittedly poor when PHP is involved).
To give you one final tip, consider the 2to3 tool created by the Python devs to translate Python 2 code to Python 3 code. Front-end-wise, it has most of the elements you need to translate Python to something. However, since the cores of Python 2 and 3 are similar, no emulation machinery is required there.
