PHP variable into Python

Error

If the Python script runs with no arguments at all, then that sys.argv[1] index is out of range.

Scripts

ExecPython.php

<?php
$var1 = "hi";
$result = shell_exec('TestingStuff.py ' . $var1);

echo "<pre>$result</pre>";

TestingStuff.py

import sys

if len(sys.argv) > 1:
    print(sys.argv[1])

Demo

Explanation

1. We will start with the Python script. The goal is, that the script prints the first argument passed to it - without running into the "IndexError: list index out of range" error.

   • python TestingStuff.py 123 we want the output 123.

2. In Python the arguments passed to the script reside in sys.argv. It's a list. sys.argv[0] is always the script name itself (here TestingStuff.py). Using the example from above sys.argv[1] is now 123.

3. Handling the edge cases: "no argument" given.

   • python TestingStuff.py

   This will result in an "IndexError: list index out of range" error, because you are trying to access a list element, which is not there. sys.argv[0] is the script name and sys.argv[1] is not set, but you are trying to print it and BAM goes the error. To avoid the error and only print the first argument, we need to make sure, that the list sys.argv contains more than one element (more than the script name). That's why i've added if len(sys.argv) > 1:.

   That means: print the first argument only, if the list has more than 1 argument.

4. Now we can test the Python script standalone - with and without arguments. And switch over to the PHP script.

5. The goal is to execute the Python script from PHP.

   PHP provides several ways to execute a script, there are for instance exec(), passthru(), shell_exec(), system(). Here we are using shell_exec(). shell_exec() returns the output of the script or command we run with it.

   In other words: if you run $result = shell_exec('php -v');, you'll get the PHP version lines in $result.

   Here we are executing the Python script TestingStuff.py and add an argument, which is $var1. It's a string and added via concatenation to the string given to shell_exec(). The $result is echoed. I wrapped pre-tags around it, because i thought this is executed in the web/browser context. If you are using the scripts only on the CLI, you might drop the pre-tags.

Execution flow

• the PHP script is executed
• shell_exec() executes the Python script
• shell_exec() returns the output of the Python script as $result
• $result is printed by PHP via echo