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Bug #75543 function "defined" should ignore class constant visibility
Submitted: 2017-11-20 13:55 UTC Modified: 2019-08-29 13:04 UTC
From: matej21 at matej21 dot cz Assigned: nikic (profile)
Status: Closed Package: Scripting Engine problem
PHP Version: 7.1.11 OS:
Private report: No CVE-ID: None
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From: matej21 at matej21 dot cz
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 [2017-11-20 13:55 UTC] matej21 at matej21 dot cz
Description:
------------
When you check if private/protected constant is defined on a class, it currently triggers a fatal error. 
For a consistency with method_exists and property_exists it should probably ignore visibility and return true

Test script:
---------------
<?php

class Foo
{
    private const BAR = 1;
}


var_dump(defined('Foo::BAR'));

Expected result:
----------------
bool(true)

Actual result:
--------------
Fatal error: Uncaught Error: Cannot access private const Foo::BAR

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 [2017-11-20 13:59 UTC] spam2 at rhsoft dot net
it should return false but not raise a fatal error at all, but there is no valid reason to return true because you can't access it outside the class
 [2017-11-20 14:47 UTC] matej21 at matej21 dot cz
The reason (as I said in the bug report) is a consistency with property_exists and method_exists, see https://3v4l.org/7PYOQ
 [2017-11-20 14:54 UTC] spam2 at rhsoft dot net
you still compare different things here and for consistency they all should return false outside of the context $this because it's simply wrong behavior leading to errors like this one which couldn't work beause for the current scope it don't exist

if(property_exists($foo, 'bar')))
{
 $foo->bar = 10;
}
_________________________________

$foo = new Foo;
var_dump(property_exists($foo, 'bar'));
var_dump(method_exists($foo, 'bar'));

defined('Foo::BAR');
_________________________________
 [2017-11-20 15:06 UTC] matej21 at matej21 dot cz
I agree with you it would be better if a current scope were taken into account for all three methods.

But you can even see in a changelog of property_exists 
( http://cz2.php.net/manual/en/function.property-exists.php ) that "This function checks the existence of a property independent of accessibility." So I suppose there was some good reason for this behavior and therefore I think "defined" function should behave in the same way.
 [2017-11-20 15:11 UTC] nikic@php.net
I believe the closer analogon to defined() on constants is isset() on properties and is_callable() on methods, both of which will take visibility into account. property_exists() and method_exists() are more like reflection methods, from a time where reflection didn't exist yet.
 [2017-11-20 15:14 UTC] spam2 at rhsoft dot net
@nikic@php.net: but in no case it has to raise a exception / fatal error because such things are typically used to test if something exists instead blindly call it and then fail - so the current behavior defeats the whole purpose
 [2017-11-20 15:19 UTC] nikic@php.net
Yes, obviously. My comment was referring to the discussion whether the return value should be true or false for an inaccessible class constant.
 [2017-11-20 17:42 UTC] cmb@php.net
-Status: Open +Status: Verified
 [2019-08-29 13:04 UTC] nikic@php.net
-Status: Verified +Status: Closed -Assigned To: +Assigned To: nikic
 [2019-08-29 13:04 UTC] nikic@php.net
This has been fixed at some point: https://3v4l.org/qUMeI
 
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