PHP Type Hints

PHP type hints allow developers to specify the expected data types of function parameters, helping to catch errors early and making code more readable. This feature is essential for ensuring that the values passed to functions align with the expected types.

Key Concepts

• Type Hinting: A method to indicate the type of argument a function should accept. If an argument of the wrong type is passed, a TypeError will be thrown.
• Supported Types: You can use type hints for:
  • Classes
  • Interfaces
  • Arrays (since PHP 7.0)
  • Callables (functions or methods that can be called)
  • Scalar types (since PHP 7.0), including:
    • int
    • float
    • string
    • bool

Basic Syntax

When defining a function, specify the type of each parameter by placing the type before the parameter name.

Example

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

In this example, the function add takes two parameters, both expected to be integers (int), and returns an integer.

Return Type Declaration

Specify the return type of a function using a similar syntax.

Example

function multiply(float $a, float $b): float {
    return $a * $b;
}

Here, the function multiply accepts two float parameters and is expected to return a float.

Error Handling

If you pass an incorrect type to a function, PHP will throw a TypeError.

Example

try {
    echo add(5, "10"); // This will cause a TypeError
} catch (TypeError $e) {
    echo "Error: " . $e->getMessage();
}

In this case, passing a string instead of an integer will result in a TypeError.

Nullable Types

Since PHP 7.1, you can allow a parameter to be null by using a question mark ? before the type.

Example

function getLength(?string $str): int {
    return $str === null ? 0 : strlen($str);
}

In this function, the parameter $str can either be a string or null.

Conclusion

Using type hints in PHP enforces data integrity and improves code clarity. By specifying expected types, you can prevent bugs and enhance the overall readability of your code.