Php :: Flex: Showing Output Of A C File In A Text Area

I managed to show the output of a shell command in TextArea of flex by calling following php file via HTTPService and then using the dataprovider attribute of TextArea to show the returned output.

<?php
$output = shell_exec('ls -l');
return $output
?>

Now i have a C file which prints some lines (by using printf command of C) when i run it in shell using

./myCfile

But following php code seems to not return anything as my TextArea remains empty

<?php
$output = shell_exec('./myCfile');
return $output
?>