Example's of PHP condition / rules creator

[Orionsbelter]

Hi Guys, 

 

I'm looking to create a module for a third party eCommerce system, that will allow the user to create rules or conditions for sending out emails to the customer. 

 

For example, the user will be able to select from dropdowns to create a rule, similar to email filtering:

 

Example 

 

IF - Cart Value - Is Greater Than - 300

 

AND - Product Category - Is Equal To - Phones 

 

FYI - All the BOLD text represents multi-select dropdowns and ITALIC text represents input boxes

I do not wish for someone to write this code for me, but would anyone know if anywhere I can learn this or does anyone of a open source script / system that I could look at. 

 

Thank you. 

[Orionsbelter]

Here is an example image of a similar feature, unfortunately this is on a closed system.