Why strict typing matters in PHP - See It in Action

Why strict typing matters

📖 Scenario: Imagine you are building a simple calculator that adds two numbers. Sometimes, the numbers might come as strings, and sometimes as integers. Without strict typing, mistakes can happen silently, causing wrong results.

🎯 Goal: You will create a PHP script that shows how strict typing helps catch errors early by enforcing the types of inputs to a function.

📋 What You'll Learn

Create a function with strict typing enabled

Define a function that adds two integers

Try calling the function with a string and an integer

Observe the error caused by strict typing

💡 Why This Matters

🌍 Real World

Strict typing is important in real-world PHP projects to avoid bugs caused by unexpected data types, especially when working with user input or external data.

💼 Career

Many PHP jobs require writing reliable and maintainable code. Understanding strict typing helps you write safer functions and avoid common errors.

1

Enable strict typing and create the add function

Write the first line declare(strict_types=1); to enable strict typing. Then create a function called add that takes two integer parameters int $a and int $b and returns their sum as an integer.

PHP

<?php
declare(strict_types=1);

function add(int $a, int $b): int {
    // Your code here
}

Need a hint?

Start your PHP file with declare(strict_types=1); to turn on strict typing. Then define the function with int type hints for parameters and return type.

2

Call the add function with integer arguments

Call the add function with two integers: 5 and 10. Store the result in a variable called $result.

PHP

<?php
declare(strict_types=1);

function add(int $a, int $b): int {
    return $a + $b;
}

// Your code here

Need a hint?

Call the function with two numbers and save the answer in $result.

3

Call the add function with a string and an integer

Call the add function with a string '5' and an integer 10. Store the result in a variable called $result2.

PHP

<?php
declare(strict_types=1);

function add(int $a, int $b): int {
    return $a + $b;
}

$result = add(5, 10);

// Your code here

Need a hint?

Try passing a string instead of an integer to see how strict typing stops this.

4

Print the results

Print the variables $result and $result2 using echo statements, each on a new line.

PHP

<?php
declare(strict_types=1);

function add(int $a, int $b): int {
    return $a + $b;
}

$result = add(5, 10);

$result2 = add('5', 10);

// Your code here

Need a hint?

Print both results. The first will show 15. The second will cause a TypeError because of strict typing.