Intersection types in PHP - Mini Project: Build & Apply

Intersection Types in PHP

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

🎯 Goal: You will create interfaces for ReportWriter and MeetingAttendee, then create a class that implements both. Finally, you will write a function that accepts only objects that satisfy both interfaces using intersection types.

📋 What You'll Learn

Create two interfaces: ReportWriter and MeetingAttendee with one method each.

Create a class Employee that implements both interfaces.

Write a function handleWorker that accepts a parameter with an intersection type of ReportWriter&MeetingAttendee.

Call the function with an Employee object and print messages from both methods.

💡 Why This Matters

🌍 Real World

Intersection types help ensure that objects passed to functions meet multiple requirements, useful in complex systems where roles overlap.

💼 Career

Understanding intersection types is important for writing clear, type-safe code in PHP, especially in large projects or when using modern PHP features.

1

Create interfaces for report writing and meeting attendance

Create two interfaces called ReportWriter and MeetingAttendee. In ReportWriter, declare a public method writeReport(). In MeetingAttendee, declare a public method attendMeeting().

PHP

<?php

// Create interface ReportWriter with method writeReport()
// Create interface MeetingAttendee with method attendMeeting()

Need a hint?

Use the interface keyword to create interfaces. Each interface should have one method declaration without a body.

2

Create a class that implements both interfaces

Create a class called Employee that implements both ReportWriter and MeetingAttendee. Implement the methods writeReport() and attendMeeting() to return the strings "Report written." and "Meeting attended." respectively.

PHP

<?php

interface ReportWriter {
    public function writeReport(): string;
}

interface MeetingAttendee {
    public function attendMeeting(): string;
}

// Create class Employee implementing ReportWriter and MeetingAttendee
// Implement writeReport() and attendMeeting() methods

Need a hint?

Use implements keyword to implement multiple interfaces. Each method must return the exact string.

3

Write a function using intersection types

Write a function called handleWorker that accepts one parameter with the intersection type ReportWriter&MeetingAttendee. Inside the function, call writeReport() and attendMeeting() on the parameter and store their results in variables $report and $meeting.

PHP

<?php

interface ReportWriter {
    public function writeReport(): string;
}

interface MeetingAttendee {
    public function attendMeeting(): string;
}

class Employee implements ReportWriter, MeetingAttendee {
    public function writeReport(): string {
        return "Report written.";
    }

    public function attendMeeting(): string {
        return "Meeting attended.";
    }
}

// Write function handleWorker with parameter type ReportWriter&MeetingAttendee
// Call writeReport() and attendMeeting() on the parameter

Need a hint?

Use the intersection type ReportWriter&MeetingAttendee in the function parameter to require both interfaces.

4

Call the function and print the results

Inside the handleWorker function, add two echo statements to print $report and $meeting each followed by a newline. Then, create an Employee object called $employee and call handleWorker($employee).

PHP

writeReport();
    $meeting = $worker->attendMeeting();
    // Print $report and $meeting with echo
}

// Create Employee object and call handleWorker

Need a hint?

Use echo to print the strings with a newline character \n. Create the object and call the function after it.