Intersection types in practice in PHP - Mini Project: Build & Apply

Intersection types in practice

📖 Scenario: Imagine you are building a simple system to manage different types of workers in a company. Some workers can both code and design. You want to make sure that certain functions only accept workers who can do both tasks.

🎯 Goal: You will create interfaces for coding and designing, then create a class that implements both. Finally, you will write a function that accepts only workers who are both coders and designers using intersection types.

📋 What You'll Learn

Create two interfaces: Coder and Designer

Create a class FullStackWorker that implements both Coder and Designer

Write a function workOnProject that accepts a parameter with an intersection type of Coder&Designer

Call the workOnProject function with an instance of FullStackWorker and print the result

💡 Why This Matters

🌍 Real World

Intersection types help ensure that objects passed to functions have multiple capabilities, useful in systems where roles overlap, like full-stack developers who code and design.

💼 Career

Understanding intersection types is important for writing clear, type-safe code in modern PHP applications, improving code quality and reducing bugs.

1

Create interfaces for coding and designing

Create two interfaces called Coder and Designer. Each interface should have one public method: code() for Coder and design() for Designer. Both methods should return a string.

PHP

<?php

// Create interface Coder with method code() returning string
// Create interface Designer with method design() returning string

Need a hint?

Use the interface keyword to create interfaces. Define methods with public visibility and specify the return type string.

2

Create a class that implements both interfaces

Create a class called FullStackWorker that implements both Coder and Designer interfaces. Implement the code() method to return the string 'Coding...' and the design() method to return the string 'Designing...'.

PHP

<?php

interface Coder {
    public function code(): string;
}

interface Designer {
    public function design(): string;
}

// Create class FullStackWorker implementing Coder and Designer
// Implement code() to return 'Coding...'
// Implement design() to return 'Designing...'

Need a hint?

Use implements keyword to implement multiple interfaces. Define both methods exactly as in the interfaces.

3

Write a function using intersection types

Write a function called workOnProject that accepts one parameter called worker with the intersection type Coder&Designer. Inside the function, return the concatenation of $worker->code() and $worker->design() separated by a space.

PHP

code() . ' ' . $worker->design()

Need a hint?

Use the intersection type Coder&Designer in the function parameter to require both interfaces.

4

Call the function and print the result

Create an instance of FullStackWorker called worker. Call the function workOnProject with worker as argument and print the returned string.

PHP

code() . ' ' . $worker->design();
}

// Create instance worker of FullStackWorker
// Print the result of workOnProject(worker)

Need a hint?

Create the object with new FullStackWorker() and use print() to show the result.