[RFC] Lazy Objects

[arnaud-lb]

https://wiki.php.net/rfc/lazy-objects

php-src/Zend/zend_lazy_objects.c

Lines 19 to 36 in fb0ced9

	/* Lazy objects are standard zend_object whose initialization is defered until
	* one of their properties backing store is accessed for the first time.
	*
	* This is implemented by using the same fallback mechanism as __get and __set
	* magic methods that is triggered when an undefined property is accessed.
	*
	* Execution of methods or virtual property hooks do not trigger initialization.
	*
	* A lazy object can be created via the Reflection API. The user specifies an
	* initializer function that is called when initialization is required.
	*
	* There are two kinds of lazy objects:
	*
	* - Ghosts: These are initialized in-place by the initializer function
	* - Proxy: The initializer returns a new instance. After initialization,
	* interaction with the proxy object are proxied to the instance.
	*
	* Internal objects are not supported.

The implementation is quite simple:

• A lazy object is just a normal object (with standard handlers, etc), with all properties unset. One could create such object in userland by using ReflectionClass::newInstanceWithoutConstructor(), followed by unset() on all properties.
• We hook in zend_std_read_property / zend_std_write_property and so on, in the code path that handles accesses to undefined properties (where we may call __get or trigger warnings). When accessing an undefined property for an object marked lazy, we call the initializer function, and restart the operation.

The engine doesn't need to be aware of lazy objects at all: everything is handled in standard object handlers.

zend_lazy_objects.c implements the logic of making an object lazy, or initializing a lazy object. Functions in these files are called by either zend_object_handlers.c, or ext/reflection/php_reflection.c.

[iluuu1994]

I have not managed to finish the review today, I'll continue tomorrow.

[iluuu1994]

LGTM otherwise!