on my system (Linux 2.6.9-023stab048.4-smp) I have installed more then one version of php. That is why the following line fails
line 68 $php_bin = trim(shell_exec('which php'));
This call detects php in /usr/local/bin/php. That's ok for most of the things I want to do because I prefer the local installed version of php. But for reasons I don't know bebot doesn't like the local installed version. Yes it's also version 5.2.x

But if you call it like this
$php_bin = trim(shell_exec('which php5'));
php5 gets found in /usr/bin/php5
That version of php works fine for bebot.

I'm not sure if I'm the only one but perhaps you can just check against php5 as default. php5 is required anyway.

This was hard to figure out because bebot does not display any error. It keeps on starting in a infinite loop.

just my two cents