Did you use something like SourceGuardian for PHP Scripts? - http://www.sourceguardian.com

Is there another OpenSource similar program?

Thanks

I find it unlikely that someone would write an opensource program who's sole purpose is to close-source php scripts and enable time-bombs, but who knows? Have a google.

Search Sourceforge for "eAccellerator" and google for Bcompiler. Don't put too much trust in this, AFAIK it still has to be decompiled before feeding it to the interpreter, at which stage you could have a look at the code. Besides that, for about every popular PHP bytecode compiler there's a decoder.

Just found this thread and it looks like interesting one.
About php encoders: I think one must go on with either
sourceguardian.com or ioncube.com
They are much more the same and you should decide yourself what to use. Ofcourse you can go with zend too, but it much much more expensive, however has less features. These three are most known and reliable. Also I've found newcomer I think: phpshield.com
They offer great price, and bytecode protection which is important
Ofcourse every protection can be cracked its just a question of resources you are ready to put in it. But I believe commercial products should use serious commercial protectors, not free ones. This gives you at least some guarantee and support after all.
Recent versions introduced obfuscation, which was firstly noticed in SourceGuardian product some years ago. This should help to protect your scripts a lot I believe.