Why type awareness matters in PHP - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code with type juggling?

Consider this PHP code snippet. What will it output?

PHP

<?php
$a = '5';
$b = 3;
echo $a + $b;
?>

A Error: Unsupported operand types

B 8

C TypeError

D '53'

💡 Hint

PHP automatically converts strings to numbers when using arithmetic operators.

PHP converts the string '5' to the integer 5 when adding to 3, so the output is 8.

❓ Predict Output

intermediate

What error occurs when adding incompatible types in PHP 8+?

What happens when you run this PHP code?

PHP

<?php
$a = 'hello';
$b = 10;
echo $a + $b;
?>

A 0

B 10

C TypeError

D hello10

💡 Hint

PHP 8+ is stricter about adding strings that cannot convert to numbers.

Adding a non-numeric string to an integer results in 0 + 10 = 10 in PHP 8+, but no TypeError is thrown.

🔧 Debug

advanced

Why does this PHP function return unexpected results?

Look at this PHP function and its output. Why does it return 'Result: 15' instead of 'Result: 510'?

PHP

<?php
function add($x, $y) {
    return $x + $y;
}

echo 'Result: ' . add('5', '10');
?>

A Because '+' concatenates strings, so it should output '510'.

B Because the function is missing a return statement.

C Because PHP throws a TypeError when adding strings.

D Because '+' adds numbers, so strings are converted to integers before addition.

💡 Hint

Think about how PHP treats '+' with string operands.

The '+' operator in PHP performs numeric addition, so string numbers are converted to integers before adding.

📝 Syntax

advanced

Which PHP code snippet correctly enforces strict typing?

Which option correctly enables strict typing and declares a function that only accepts integers?

A

<?php
declare(strict_types=0);
function multiply(int $a, int $b): int {
    return $a * $b;
}
?>

B

<?php
function multiply(int $a, int $b): int {
    return $a * $b;
}
declare(strict_types=1);
?>

C

<?php
declare(strict_types=1);
function multiply(int $a, int $b): int {
    return $a * $b;
}
?>

D

<?php
strict_types=1;
function multiply(int $a, int $b): int {
    return $a * $b;
}
?>

💡 Hint

Strict typing must be declared at the top of the file before any code.

Option C correctly places declare(strict_types=1); at the top before any code, enabling strict typing.

🚀 Application

expert

What is the output of this PHP code using union types and strict typing?

Given this PHP code, what will it output?

PHP

<?php
declare(strict_types=1);
function formatValue(int|string $value): string {
    return match(gettype($value)) {
        'integer' => "Number: $value",
        'string' => "Text: $value",
        default => 'Unknown',
    };
}

echo formatValue(42) . ', ' . formatValue('hello');
?>

A Number: 42, Text: hello

B 42, hello

C Text: 42, Number: hello

D TypeError

💡 Hint

Look at how match uses gettype to decide the output string.

The function returns 'Number: 42' for integer input and 'Text: hello' for string input, joined by a comma.