ReflectionClass::newLazyGhost

(PHP 8 >= 8.4.0)

ReflectionClass::newLazyGhost — Creates a new lazy ghost instance

Description

public ReflectionClass::newLazyGhost(callable $initializer, int $options = 0): object

Creates a new lazy ghost instance of the class, attaching the initializer to it. The constructor is not called, and properties are not set to their default value. However, the object will be automatically initialized by invoking the initializer the first time its state is observed or modified. See Initialization Triggers and Initialization Sequence.

Parameters

initializer

The initializer is a callback with the following signature:

initializer(object $object): void

object: The object being initialized. At this point, the object is no longer marked as lazy, and accessing it does not trigger initialization again.

The initializer function must return null or no value.

options

options can be a combination of the following flags:

ReflectionClass::SKIP_INITIALIZATION_ON_SERIALIZE: By default, serializing a lazy object triggers its initialization. Setting this flag prevents initialization, allowing lazy objects to be serialized without being initialized.

Return Values

Returns a lazy ghost instance. If the object has no properties, or if all its properties are static or virtual, a normal (non-lazy) instance is returned. See also Lifecycle of Lazy Objects.

Errors/Exceptions

An Error if the class is internal or extends an internal class except stdClass.

Examples

Example #1 Basic usage

<?php

class Example {
    public function __construct(public int $prop) {
        echo __METHOD__, "\n";
    }
}

$reflector = new ReflectionClass(Example::class);
$object = $reflector->newLazyGhost(function (Example $object) {
     $object->__construct(1);
});

var_dump($object);
var_dump($object instanceof Example);

// Triggers initialization, and fetches the property after that
var_dump($object->prop);

?>

The above example will output:

lazy ghost object(Example)#3 (0) {
  ["prop"]=>
  uninitialized(int)
}
bool(true)
Example::__construct
int(1)

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User Contributed Notes 1 note

down

dave1010 at gmail dot com ¶

1 month ago

Simple helper function that makes it easier to understand:

<?php

function createLazyGhost(
    string $class,
    ?callable $initializer = null,
    ?array $propertySetterCallables = null
): object {
    $reflection = new ReflectionClass($class);

    return $reflection->newLazyGhost(function (object $object) use ($initializer, $propertySetterCallables) {
        // Initialize via the main initializer if provided
        if ($initializer) {
            $initializer($object);
        }

        // Set properties using the callables if provided
        if ($propertySetterCallables) {
            foreach ($propertySetterCallables as $property => $callable) {
                if (is_callable($callable)) {
                    $object->$property = $callable();
                }
            }
        }
    });
}

?>

This supports using either a main object initializer and/or property initializers.

Here's an example, where generating order IDs and calculating totals is considered expensive, so we only do it when necessary:

<?php

class Order {
    public string $orderId = '';
    public float $total = 0.0;
}

$initializer = function (Order $order) {
    $order->orderId = 'ORD12345';
};

$propertySetters = [
    'total' => fn() => 200.75,
];

// Lazy ghost with both an initializer and property callables
$lazyOrder = createLazyGhost(Order::class, $initializer, $propertySetters);

// We can now use $lazyOrder as normal, even though the properties haven't been calculated yet.

// Do something that triggers initialization
echo $lazyOrder->orderId . PHP_EOL;
echo $lazyOrder->total . PHP_EOL;

?>