php.net |  support |  documentation |  report a bug |  advanced search |  search howto |  statistics |  random bug |  login
Request #78480 The typed properties miss an important "function"
Submitted: 2019-08-30 21:27 UTC Modified: 2019-11-07 11:03 UTC
From: manchokapitancho at gmail dot com Assigned:
Status: Open Package: Scripting Engine problem
PHP Version: 7.4.0beta4 OS:
Private report: No CVE-ID: None
View Add Comment Developer Edit
Welcome! If you don't have a Git account, you can't do anything here.
You can add a comment by following this link or if you reported this bug, you can edit this bug over here.
(description)
Block user comment
Status: Assign to:
Package:
Bug Type:
Summary:
From: manchokapitancho at gmail dot com
New email:
PHP Version: OS:

 

 [2019-08-30 21:27 UTC] manchokapitancho at gmail dot com
Description:
------------
The new PHP 7.4 feature - typed properties is a great addition to the language.
As a side effect it adds a brand new state of the class/object properties - initialized=yes/no.
If one tries to access an uninitialized property, a TypeError is being thrown.
isset($object->prop) does not trigger TypeError but it returns false if $object->prop is NULL.
The suggested check is only indirectly possible via the long construct
(new ReflectionProperty(<name>::class, '<prop>'))->isInitialized($obj)

On the other side, unset works perfectly well and returns a property back into the uninitialized state.

This write-only asymmetry is not consistent and I would expect a language construct similar to isset [e.g. is_initialized($obj->prop)] that handles this case.

Test script:
---------------
class test {
	public ?int $prop;
}
$obj = new test;

var_dump(isset($obj->prop));
var_dump(is_initialized($obj->prop));

$obj->prop = null;

var_dump(isset($obj->prop));
var_dump(is_initialized($obj->prop));



Expected result:
----------------
false
false
false
true

Actual result:
--------------
false
<missing>
false
<missing>

Patches

Add a Patch

Pull Requests

Add a Pull Request

History

AllCommentsChangesGit/SVN commitsRelated reports
 [2019-08-31 11:42 UTC] nikic@php.net
What's your use-case?

A language construct for this is very unlikely, but if this is a common and performance-critical operation, a plain function could be provided in lieu of going through reflection.
 [2019-08-31 14:05 UTC] manchokapitancho at gmail dot com
A simplified use case would be:

//orm with lazy loading from DB
class something {
 public ?<class|self> $parent;
....
function getParent() {
 if (! is_initialized($this->parent)) {
 $this->parent = //fetch from DB; value could be NULL
 }
 return $this->parent;
}
...
}


A plain function is indeed possible but the call parameters should be ($obj, 'prop) since ($obj->prop) would throw TypeError.
 [2019-09-08 18:10 UTC] jhdxr@php.net
You can use `__get` to check if it's initialized. 

see the Overloaded Properties section of the RFC(https://wiki.php.net/rfc/typed_properties_v2) as an example.
 [2019-09-09 18:10 UTC] manchokapitancho at gmail dot com
I know that I can use __get but:
1. this is a workaround (which is also not simpler than a ReflectionProperty call).
2. this is only possible if the developer has control over the class. A counterexample would be a typed property in a class exposed by a third party library.

Once again: the target is "if (!is_initialized($obj->prop)) { ... }" similar to 
"if (!isset($obj->prop)) { ... }". Isset would not generate a notice if the property is not defined and similarly is_initialized should not trigger a TypeError if $obj->prop has not been yet initialized.
 [2019-11-07 11:03 UTC] nikic@php.net
-Type: Bug +Type: Feature/Change Request
 
PHP Copyright © 2001-2019 The PHP Group
All rights reserved.
Last updated: Thu Dec 05 22:01:23 2019 UTC