PHP Interfacing with Python -- Getting Null Return Value

I lifted some code off of StackOverflow to test some very basic PHP / Python integration, as I would like to eventually create a web interface for a Python machine learning platform I've been testing for a while now.

The code is as follows below:

PHP:

<?php

    $data = array('1', '2', '3');
    $result = shell_exec('python "C:\Program Files (x86)\Zend\Apache24\htdocs\Machine-Learning-Python-Integration\phptransfertest.py" ' . escapeshellarg(json_encode($data)));

    $resultData = json_decode($result, true);

    var_dump($resultData);

?>

Python:

import sys
import json

try:
    data = json.loads(sys.argv[1])

except:
    print "ERROR"
    sys.exit(1)

result = {'status': 'Yes!'}

print json.dumps(result)

But when I load this up in a browser, it only outputs NULL. I am unsure how to properly pass variables and files between Python and PHP, and most guides I have found tend to give me a NULL error.