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

Union types in practice

📖 Scenario: You are building a simple PHP program to handle user input that can be either a string or an integer. This is common when dealing with form data where users might enter numbers or text.

🎯 Goal: Create a PHP function that accepts a parameter which can be either an int or a string using union types. The function will return a message describing the type and value of the input.

📋 What You'll Learn

Create a function called describeInput that accepts a parameter with a union type int|string.

Inside the function, use is_int() and is_string() to check the type of the input.

Return a string message describing the input type and value.

Call the function with both an integer and a string and print the results.

💡 Why This Matters

🌍 Real World

Handling user input that can be multiple types is common in web forms and APIs. Union types help make your code clear and safe.

💼 Career

Understanding union types is important for writing modern PHP code that is robust and easy to maintain, a skill valued in backend development jobs.

1

Create the describeInput function with union type parameter

Write a PHP function called describeInput that accepts one parameter named $input with the union type int|string. Inside the function, just return an empty string "" for now.

PHP

<?php

function describeInput(int|string $input): string {
    // Your code here
}

Need a hint?

Use the syntax function describeInput(int|string $input): string to declare the function with a union type parameter.

2

Add type checks inside describeInput

Inside the describeInput function, add an if statement to check if $input is an integer using is_int($input). If true, return the string "Input is an integer: " concatenated with the value of $input. Add an elseif to check if $input is a string using is_string($input) and return "Input is a string: " concatenated with $input. Keep the function signature and the empty return removed.

PHP

<?php

function describeInput(int|string $input): string {
    // Your code here
}

Need a hint?

Use is_int() and is_string() to check the type and return the appropriate message.

3

Call describeInput with an integer and a string

After the function, write two lines of code that call describeInput with the integer 42 and the string "hello". Store the results in variables $resultInt and $resultStr respectively.

PHP

<?php

function describeInput(int|string $input): string {
    if (is_int($input)) {
        return "Input is an integer: " . $input;
    } elseif (is_string($input)) {
        return "Input is a string: " . $input;
    }
}

// Your code here

Need a hint?

Call the function with 42 and "hello" and save the results in $resultInt and $resultStr.

4

Print the results

Print the variables $resultInt and $resultStr each on its own line using echo. Use "\n" for new lines.

PHP

<?php

function describeInput(int|string $input): string {
    if (is_int($input)) {
        return "Input is an integer: " . $input;
    } elseif (is_string($input)) {
        return "Input is a string: " . $input;
    }
}

$resultInt = describeInput(42);
$resultStr = describeInput("hello");

// Your code here

Need a hint?

Use echo $resultInt . "\n"; and echo $resultStr . "\n"; to print each result on a new line.