What is the output of this PHP 8+ code involving anonymous classes and closures? Explain the scope and binding behavior.

Code Analysis:

$multiplier = 10;

$calculator = new class($multiplier) {
    private $factor;
    
    public function __construct($factor) {
        $this->factor = $factor;
    }
    
    public function createMultiplier() {
        return function($value) {
            return $value * $this->factor;
        };
    }
    
    public function createStaticMultiplier() {
        $factor = $this->factor;
        return static function($value) use ($factor) {
            return $value * $factor;
        };
    }
};

$multiply1 = $calculator->createMultiplier();
$multiply2 = $calculator->createStaticMultiplier();

echo $multiply1(5) . "\n";
echo $multiply2(5) . "\n";

// Serialize test
try {
    serialize($multiply1);
    echo "multiply1 serializable\n";
} catch (Exception $e) {
    echo "multiply1 not serializable\n";
}

try {
    serialize($multiply2);
    echo "multiply2 serializable\n";
} catch (Exception $e) {
    echo "multiply2 not serializable\n";
}

Output:

50
50
multiply1 not serializable
multiply2 serializable

Explanation:

1. Anonymous Class Behavior:

• Anonymous class captures $multiplier in constructor
• Creates instance with private $factor = 10
• Class has unique generated name like class@anonymous

2. Closure Binding:

• createMultiplier(): Returns non-static closure bound to $this
• createStaticMultiplier(): Returns static closure with captured variable
• Both access the same value but through different mechanisms

3. Serialization Behavior:

• $multiply1: Cannot serialize - bound to object instance
• $multiply2: Can serialize - static closure with captured variables

Advanced Closure Concepts:

// Closure binding manipulation
$closure = function() {
    return $this->factor;
};

// Bind to different object
$boundClosure = $closure->bindTo($calculator, $calculator);
echo $boundClosure(); // 10

// Static binding
$staticClosure = Closure::bind($closure, null, get_class($calculator));
// $staticClosure(); // Error: $this not available in static context

Performance Considerations:

• Object-bound closures keep object in memory
• Static closures are more memory efficient
• Use static closures when $this is not needed