Interface constants in PHP - Mini Project: Build & Apply

Interface constants

📖 Scenario: You are building a simple PHP program to manage user roles in a system. Each role has a fixed access level represented by a number. You want to use interface constants to keep these access levels organized and easy to use.

🎯 Goal: Create an interface with constants for user roles and their access levels. Then, use these constants in a class to display the access level for a specific role.

📋 What You'll Learn

Create an interface called UserRoles with constants ADMIN, EDITOR, and VIEWER having values 3, 2, and 1 respectively.

Create a class called AccessControl with a method getAccessLevel that takes a role constant and returns its access level.

Use the interface constants inside the class method to return the correct access level.

Print the access level for the EDITOR role.

💡 Why This Matters

🌍 Real World

Interface constants help keep fixed values organized and easy to maintain in large PHP applications, such as user roles or configuration settings.

💼 Career

Understanding interface constants is useful for PHP developers working on projects that require clear, reusable, and consistent values across multiple classes.

1

Create the interface with constants

Create an interface called UserRoles with constants ADMIN set to 3, EDITOR set to 2, and VIEWER set to 1.

PHP

<?php

// Create interface UserRoles with constants ADMIN=3, EDITOR=2, VIEWER=1
// Your code here

Need a hint?

Use the interface keyword and define constants inside it using const NAME = value;.

2

Create the AccessControl class with getAccessLevel method

Create a class called AccessControl with a public method getAccessLevel that takes a parameter $role and returns the value of $role.

PHP

<?php

interface UserRoles {
    const ADMIN = 3;
    const EDITOR = 2;
    const VIEWER = 1;
}

// Create class AccessControl with method getAccessLevel($role) that returns $role
// Your code here

Need a hint?

Define a class with a public method that returns the input parameter.

3

Use interface constants in the method call

Create an instance of AccessControl called $accessControl. Then call the method getAccessLevel on $accessControl with the argument UserRoles::EDITOR and store the result in a variable called $level.

PHP

<?php

interface UserRoles {
    const ADMIN = 3;
    const EDITOR = 2;
    const VIEWER = 1;
}

class AccessControl {
    public function getAccessLevel($role) {
        return $role;
    }
}

// Create $accessControl instance and call getAccessLevel with UserRoles::EDITOR
// Store result in $level
// Your code here

Need a hint?

Create an object with new and call the method using -> operator with the interface constant.

4

Print the access level

Print the value of the variable $level using echo.

PHP

getAccessLevel(UserRoles::EDITOR);

// Print the value of $level
// Your code here

Need a hint?

Use echo $level; to display the access level.