Structure for PHP project and use of eval() function

Question:

I need to develop an application that fits several projects with common features, however each one has several specific rules.

What I need is a structure that allows me to easily change these rules, in this case I chose to save the rules in the database and use the eval() function to execute the code in the application, however, I don't think this would be the best option to get the result I need (not even the safest, even if the rules are encrypted).

Structure I am using now is:

app
    controller [controllers]
    model [models] [aqui são aplicados as regras do banco de dados]
    entity [entidades do banco de dados]
    repository [model <=> entity]
    helper [helpers]
    view [views]
    theme [themes]
config
    [configurações da aplicação]
data
    logs [app logs]
    cache [view cache]
public 
    [módulos angular, assets, index.php e .htaccess]
vendor
    [libraries, app-core]

The rules would be applied something like this:

// Random key (config)
define('PRIVATE_KEY', 'SECURE_RANDOM_KEY');

// antes

foreach ( regras as regra )
    parse(decode(regra, PRIVATE_KEY));

// continua execução

Any ideas on how I could improve this?

Answer:

Why don't you use classes? For example:

interface Regras {
    public function execute();
}

class RegrasApp implements Regras {
    public function execute() {
        // suas regras aqui
    }
}

$regras = new RegrasApp();
$regras->execute();