What's the best way to code and distribute free trial license?

I sell a webscript which is written in the php language. What I want to do is create a license for each user and limit the script installation to one domain only.

Also, I want to distribute this same script as a free trial for 15 days. After that the user must upgrade. The script will call home to verify if the user has valid record in our server or not.

What's the best and "hard to crack" way to distribute license in that way

 

Anything you do is pretty much going to be crackable. What most applications do is encode parts of the script with zend or another encoder.

 

try using such a script http://www.phplicensescript.com/

 

Actually i'm developing that kind of script.
But it is still under development.
Basically make the license system and encrypt all the php source file.
And php client will check the license to the server and permit it.

 

I've made programs like this before, what I done was to create a few checks in the script which check with my server if the person holds a valid licence. I encoded all that section, worked fine for me.

Glen