class AGI_AsteriskManager can not be initiated

I've written an AGI-Script with phpagi 2x, Asterisk 1.8x and php 5.2.6.
With phpagi.php all is working well. But, in the moment where I'am trying to initiate AGI_AsteriskManager, the AGI-Sript returns/ends immidiately.

My code:

#!/usr/bin/php -q
<?php
set_time_limit(30);
require('phpagi.php');
error_reporting(E_ALL);
$dbfile="blabla";
$gen_prefs = array();
$agi = new AGI();

$am = $agi->new_AsteriskManager();

... more stuff, but teh script ends here for unknown reasons :-(
?>

There is no error message ... nothing is logged...nothing....have someone an idea what the problem could be ?

The files phpagi.php and phpagi-asmanager.php are in the same directory.

It would be really great if someone could give me a hint in the right direction.

Thanks in advance,

Thomas.