Explicit null handling

Always be explicit and consistent when handling null values to improve code clarity and prevent subtle bugs. This applies to null checks, nullable type declarations, and function parameters.

For null checks:

• Use explicit comparisons with null rather than relying on truthiness checks
• Write null !== $variable or $variable === null instead of just if ($variable)
• Avoid variable assignments within conditional statements when checking for null

For type declarations:

• Always use the nullable operator (?) for parameters and return types that can be null
• Make docblocks consistent with type declarations by documenting nullable types
• Ensure parameters with null defaults are always declared as nullable

For function parameters:

• If a parameter is optional and can be null, make it both nullable and provide a default
• Be consistent with parameter nullability across similar functions

// Bad
public function doSomething($client)
{
    if ($client) {
        // ...
    }
}

// Good
public function doSomething(?ClientInterface $client = null): ?string
{
    if (null !== $client) {
        // ...
    }
}

This pattern makes intent clear, improves static analysis capabilities, and provides better autocomplete support in IDEs. It also prevents confusion between false, empty strings, zero, and null values in conditionals.