[eluser]TheFuzzy0ne[/eluser]
I think so.
Code:
define('IN_PHPBB', TRUE);
include 'path_to_phpbb3/includes/functions.php';
$password = 'my-secret-password';
$pw_hash = phpbb_hash($password);
echo $pw_hash;
I'm not sure if this will work. You may get unexpected results, but there's only one way to find out.
If you wanted to, you could easily make this a part of the PHPBB3 library.