java - PHP exec() not getting $output -

i made jar file (stringgenerator.jar) gets command line parameter, generates string based on parameter , prints string on standard output. this:

stringgenerator.java

public class stringgenerator {     public static void main(string[] args) {         string s = args[0];         // ... modifies s ...         system.out.println(s);     } } 

now need php code executes stringgenerator.jar, gets value of s , redirects user.

i'm trying this:

index.php

<?php     exec('java -jar stringgenerator.jar $parameter', $output);     header("location: /someurl/$output[0]"); ?> 

but $output empty array (and therefore user redirected "/someurl/" ). how can work?

thank you.

try approach:

<?php     exec('java -jar stringgenerator.jar $parameter 2>&1', $output);     header("location: /someurl/$output[0]"); ?> 

2>&1ensures output goes php handler.