Hi,
I have been a PHP developer for 13 years and have experience building enterprise applications.

What framework are you using? Most PHP frameworks have a built in authentication and authorization mechanism. For example, Yii has a builtin RBAC system that allow you to define a hierarchical permission system.

If you're not using a framework or you just want to implement your own system for whatever reason then you can utilize Object Oriented Design and implement a Base controller (if MVC) that checks the permission for each request. That won't use a lot of if statements.

Probably need more info, to give definitive guidance. Hope that helps.