(PHP 8 >= 8.4.0)
ReflectionClass::initializeLazyObject — Forces initialization of a lazy object
   Forces initialization of the specified object. This
   method has no effect if the object is not lazy or has already been
   initialized. Otherwise, initialization proceeds as described in the
   Initialization
   Sequence.
  
Note: In most cases, calling this method is unnecessary, as lazy objects initialize themselves automatically when their state is observed or modified.
object
   If object is a lazy proxy, returns its real instance.
   Otherwise, returns object itself.
  
Example #1 Basic usage
<?php
class Example
{
    public function __construct(public int $prop) {
    }
}
$reflector = new ReflectionClass(Example::class);
$object = $reflector->newLazyGhost(function ($object) {
    echo "Initializer called\n";
    $object->__construct(1);
});
var_dump($object);
$reflector->initializeLazyObject($object);
var_dump($object);
?>The above example will output:
lazy ghost object(Example)#3 (0) {
  ["prop"]=>
  uninitialized(int)
}
Initializer called
object(Example)#3 (1) {
  ["prop"]=>
  int(1)
}
