Python / Selenium / PhantomJS: "Unable to start phantomjs with ghostdriver."

I ran into the same issue. I needed to provide the full path to the exe, as described in the documentation:

from selenium import webdriver
driver = webdriver.PhantomJS(executable_path='C:\phantomjs-1.9.2\phantomjs.exe')

You need to modify ...\Python27\Lib\site-packages\selenium-2.39.0-py2.7.egg\selenium\webdriver\phantomjs\service.py

This google code page would help.