Executing Python Script with PHP Variables

Question

I am writing a simple application that uses information from a form, passes it through $_POST to a PHP script that executes a python script and outputs the results. The problem I am having is that my python script is not actually running with the arguments being passed in.

process3.php file:

<?php
     $start_word = $_POST['start'];
     $end_word = $_POST['end'];
     echo "Start word: ". $start_word . "<br />";
     echo "End word: ". $end_word . "<br />";
     echo "Results from wordgame.py...";
     echo "</br>";
     $output = passthru('python wordgame2.py $start_word $end_word');
     echo $output;
?>

Output:

Start word: dog
End word: cat
Results from wordgame.py...
Number of arguments: 1 arguments. Argument List: ['wordgame2.py']

At the top of my wordgame2.py, I have the following (for debugging purposes):

#!/usr/bin/env python
import sys
print 'Number of arguments:', len(sys.argv), 'arguments.'
print 'Argument List:', str(sys.argv)

Why isn't the number of arguments being passed = 3? (Yes, my form does send the data correctly.)

Any help is greatly appreciated!

Edit: I might add that it does run when I explicitly tell it the start and end word... something like this:

$output = passthru('python wordgame2.py cat dog');
echo $output

Solution 1

Update -

Now that I am aware of PHP, the mistake lies in using the single-quotes '. In PHP, single quoted strings are considered literals, PHP does not evaluate the content inside it. However, double quoted " strings are evaluated and would work as you are expecting them to. This is beautifully summarized in this SO answer. In our case,

$output = passthru("python wordgame2.py $start_word $end_word");

would work, but the following won't -

$output = passthru('python wordgame2.py $start_word $end_word');

Original answer -

I think the mistake lies in

$output = passthru("python wordgame2.py $start_word $end_word");

Try this

$output = passthru("python wordgame2.py ".$start_word." ".$end_word);

Solution 2

Thank you for your contributions. I have figured out my problem with this simple fix:

$command = 'python wordgame2.py ' . $start_word . ' ' . $end_word;
$output = passthru($command);

In order for passthru to properly handle the php variables, it needs to be concatenated into the string before executing.

Comments

[aIKid]

Instead of posting your answer, which is ashish's answer, please accept his answer.

[Micah]

I had posted this before I saw his answer. Please look at the time stamp.

[scandinavian_]

Wouldn't the obvious solution be using " instead of '? No need to concatenate when " does variable interpolation.

[shad0w_wa1k3r]

Hmm...am not much familiar with php (none at all), so only my answer begins with I think...

[shad0w_wa1k3r]

Actually, I answered 7 seconds before :) The downvote was unnecessary/unverified.

[Terry]

Also, probably good to use escapeshellarg() on the two arguments passed in when concatenating.