PHP Refactoring

Overview

Apply systematic refactoring techniques to improve PHP code structure while preserving behavior. Supports modern PHP 8.1+ features and common design patterns.

Refactoring Catalog

Extract Method

When a code fragment can be grouped together:

// Before
function printReport(): void {
    // print header
    echo "=== Report ===\n";
    echo "Date: " . date('Y-m-d') . "\n";

    // print body
    foreach ($items as $item) {
        echo "{$item['name']}: {$item['value']}\n";
    }
}

// After
function printReport(): void {
    $this->printHeader();
    $this->printBody($items);
}

Replace Conditional with Polymorphism

// Before
function calculateArea(string $shape, float ...$dims): float {
    return match($shape) {
        'circle' => M_PI * $dims[0] ** 2,
        'rectangle' => $dims[0] * $dims[1],
        'triangle' => 0.5 * $dims[0] * $dims[1],
    };
}

// After: Use interface + implementations
interface Shape {
    public function area(): float;
}

Introduce Parameter Object

When multiple parameters travel together:

// Before
function createUser(string $name, string $email, string $role, int $age): User

// After
function createUser(CreateUserRequest $request): User

Use PHP 8.1+ Features

• •Constructor promotion
• •Readonly properties
• •Enums instead of string constants
• •Named arguments for clarity
• •Fibers for async operations
• •First-class callable syntax
• •Intersection types
• •Match expressions

Rules

1. •Never change behavior - refactoring preserves existing functionality
2. •Small steps - make one refactoring at a time
3. •Test between steps - run tests after each change
4. •Commit frequently - each refactoring should be a separate commit
5. •Explain rationale - document why each change improves the code

Scripts

Use scripts/detect-smells.php to identify common code smells in a file or directory.