Type declarations for parameters in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with typed parameters

What is the output of this PHP code when calling greet('Alice')?

PHP

<?php
function greet(string $name) {
    return "Hello, $name!";
}
echo greet('Alice');

A Hello, Alice!

B Hello, !

C TypeError

D Fatal error

💡 Hint

The function expects a string parameter and returns a greeting.

The function greet requires a string parameter. Passing 'Alice' is valid, so it returns 'Hello, Alice!'.

❓ Predict Output

intermediate

Type error with wrong parameter type

What happens when this PHP code runs?

PHP

<?php
function square(int $num) {
    return $num * $num;
}
echo square('5');

A 25

B TypeError

C 5

D Warning: A non-numeric value encountered

💡 Hint

PHP can convert strings to integers automatically in some cases.

PHP converts the string '5' to integer 5 automatically, so the function returns 25.

❓ Predict Output

advanced

Return type declaration with parameter types

What is the output of this PHP code?

PHP

<?php
function add(float $a, float $b): float {
    return $a + $b;
}
echo add(2, 3.5);

A 5

B TypeError

C 5.5

D Fatal error

💡 Hint

PHP converts integers to floats when needed for float parameters.

The integer 2 is converted to float 2.0, so the sum is 5.5 as a float.

❓ Predict Output

advanced

Nullable type declaration for parameter

What is the output of this PHP code?

PHP

<?php
function welcome(?string $name) {
    if ($name === null) {
        return 'Welcome, guest!';
    }
    return "Welcome, $name!";
}
echo welcome(null);

A Fatal error

B Welcome, !

C TypeError

D Welcome, guest!

💡 Hint

The question mark before string means the parameter can be null.

The parameter accepts null, so the function returns 'Welcome, guest!' when null is passed.

❓ Predict Output

expert

Class type declaration for parameter

What is the output of this PHP code?

PHP

<?php
class User {
    public string $name;
    public function __construct(string $name) {
        $this->name = $name;
    }
}
function greetUser(User $user) {
    return "Hello, {$user->name}!";
}
$user = new User('Bob');
echo greetUser($user);

A TypeError

B Hello, Bob!

C Hello, !

D Fatal error

💡 Hint

The function expects an object of class User.

The object $user is an instance of User with name 'Bob', so the function returns 'Hello, Bob!'.