In PHP 7.0:
$a = 'this';
return isset( $$a );
// returns true
But in PHP 7.1:
$a = 'this';
return isset( $$a );
// returns false
Does anyone know why this happens?
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Moein Pakkhesal
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1Really? https://3v4l.org/ARNhT – Andreas Jun 25 '18 at 11:32
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@Andreas yes, and the PHP version I used was 7.0.8 – Moein Pakkhesal Jun 25 '18 at 11:36
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But you see this? *Output for 5.6.30, hhvm-3.18.5 - 3.22.0, 7.0.30 - 7.3.0alpha1*? – Andreas Jun 25 '18 at 11:37
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1@Andreas, the question probably means something like https://3v4l.org/kQ271. – jh1711 Jun 25 '18 at 11:39
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And for comparison: https://3v4l.org/RDJa0 – Progrock Jun 25 '18 at 11:42
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@jh1711 yes, that's what I meant – Moein Pakkhesal Jun 25 '18 at 11:43
1 Answers
7
This is related to this change in 7.1:
Inconsistency fixes to
$thisWhilst
$thisis considered a special variable in PHP, it lacked proper checks to ensure it wasn't used as a variable name or reassigned. This has now been rectified to ensure that$thiscannot be a user-defined variable, reassigned to a different value, or be globalised.
This RFC explains it in more detail, though it also says:
Disable ability to re-assign
$thisindirectly through$$An attempt to re-assign
$thisthrough$$assignment will lead to throwing of Error exception.$a = "this"; $$a = 42; // throw new Error("Cannot re-assign $this")It's still possible to read
$thisvalue through$$.
(Emphasis mine.)
isset seems to have its own special treatment of $$ for $this which prohibits it from seeing it. I'm not sure if that's intentional or a byproduct of these changes.
deceze
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