Why strict typing matters in PHP - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output when strict typing is enabled?

Consider this PHP code with strict typing enabled. What will it output?

PHP

<?php
declare(strict_types=1);
function addInts(int $a, int $b): int {
    return $a + $b;
}
echo addInts(5, '10');

A 15

B 5

C 510

D TypeError

💡 Hint

Strict typing enforces exact types for function parameters.

With strict typing enabled, passing a string where an int is expected causes a TypeError.

❓ Predict Output

intermediate

What happens without strict typing?

What will this PHP code output when strict typing is not enabled?

PHP

<?php
function addInts(int $a, int $b): int {
    return $a + $b;
}
echo addInts(5, '10');

A TypeError

B 510

C 15

D 5

💡 Hint

Without strict typing, PHP tries to convert types automatically.

PHP converts the string '10' to integer 10 automatically, so the sum is 15.

🔧 Debug

advanced

Identify the error with strict typing

What error will this code produce when strict typing is enabled?

PHP

<?php
declare(strict_types=1);
function greet(string $name): string {
    return 'Hello, ' . $name;
}
echo greet(123);

A TypeError

B Hello, 123

C Parse error

D Fatal error: Uncaught Error

💡 Hint

Check the type of argument passed to the function.

Strict typing requires the argument to be a string. Passing an integer causes a TypeError.

🧠 Conceptual

advanced

Why use strict typing in PHP?

Which of the following is the best reason to enable strict typing in PHP?

A It makes PHP run faster by skipping type checks

B It helps catch type-related bugs early by enforcing exact types

C It allows mixing types freely without errors

D It automatically converts all types to strings

💡 Hint

Think about how strict typing affects error detection.

Strict typing forces exact types, so bugs from wrong types are caught early, improving code safety.

❓ Predict Output

expert

What is the output with mixed types and strict typing?

Given strict typing is enabled, what will this code output?

PHP

<?php
declare(strict_types=1);
function multiply(float $a, float $b): float {
    return $a * $b;
}
$result = multiply(3, 2.5);
echo gettype($result) . ': ' . $result;

A float: 7.5

B int: 7

C TypeError

D string: 7.5

💡 Hint

Check how PHP handles integers passed to float parameters with strict typing.

PHP allows int to float conversion in strict mode for parameters typed as float, so result is float 7.5.