Python script is not executed from PHP script on local server

I am using PHP and XAMPP. I have enabled port localhost:8080 and I want to execute a python script (Main.py) from my PHP script (index.php). My PHP script is located at:

/Users/User/.bitnami/stackman/machines/xampp/volumes/root/htdocs/index.php

and the Python script is located at:

/Users/User/.bitnami/stackman/machines/xampp/volumes/root/htdocs/Main.py.

My Python script is the following:

print('Hello World')

My PHP script is the following:

<?php

$output = exec('/usr/local/bin/python3 /Users/User/.bitnami/stackman/machines/xampp/volumes/root/htdocs/Main.py ' . ' 2>&1');
var_dump($output);

?>

(/usr/local/bin/python3 is the output of which python3 at the terminal)

However, the output that I am getting at localhost:8080 is:

string(40) "sh: 1: /usr/local/bin/python3: not found"

I have also tested different variations of my line with exec() by writing for example exec('/Users/User/.bitnami/stackman/machines/xampp/volumes/root/htdocs/Main.py ' . ' 2>&1') but nothing returns the right output.

What am I doing wrong and how can I fix it?

I am aware of similar posts on StackOverflow (Running a Python script from PHP, Can't execute Python script from PHP document, Python Script Failing to Execute from PHP exec(), How to properly call Python 3 script from PHP?) but none of this works as such for me.

I am wondering if my problem is related to the fact that I did not make any configuration to run the Python script on XAMPP as it is described at some posts here (Running Python scripts with Xampp).