? PHP OOP Type Hinting

? Quick Overview

Type Hinting in PHP allows developers to specify the expected data type of parameters and return values. This improves code reliability, readability, and prevents invalid data from entering functions or methods.

? Key Concepts

Primitive types: int, float, string, bool
Array type: array
Object type: specific class names
Union types: int|string
Nullable types: ?int
Return type declarations

? Syntax & Theory

Type hints are placed before parameters, and return types are declared after the method signature using a colon. PHP validates the type at runtime.

? Basic Code Example

? View Code Example

// Basic type hinting with parameters and return types
add(5, 10);
echo "
";
echo $calc->greet("Alice");
?>

? Object Type Hinting

? View Code Example

// Enforcing object types in method parameters
name = $name;
}
}

class UserService {
public function printUser(User $user): void {
echo "User: " . $user->name;
}
}

$user = new User("Bob");
$service = new UserService();
$service->printUser($user);
?>

? Advanced Examples

? View Code Example

// Union and nullable type hinting
double(5);
echo "
";
$math->setAge(null);
?>

? Live Output & Explanation

The output shows how PHP strictly enforces data types and safely handles multiple allowed types or nullable values.

? Use Cases

Validating user input
Building large OOP-based applications
Reducing runtime bugs
Improving IDE autocomplete and documentation

✅ Tips & Best Practices

Use declare(strict_types=1); for strict checking
Always define return types
Use union and nullable types carefully
Keep method signatures clean and clear

? Try It Yourself

Create a function using int parameters and test invalid values
Write a class that only accepts object parameters
Experiment with union types
Test nullable types using null