Hi all,
There is currently an odd inconsistency when using the decrement
operator on a null variable:
$a = null; $a=$a+1; // int(1)
$a = null; $a+=1; // int(1)
$a = null; ++$a; // int(1)
$a = null; $a=$a-1; // int(-1)
$a = null; $a-=1; // int(-1)
$a = null; --$a; // null
I would like to propose changing this behaviour for PHP 8, so that --$a
would give int(-1), as I believe it is simply a long-standing bug.
This has been raised as a bug at least three times [1][2][3] but closed
as documented behaviour / too much of a BC break. It is documented in
the manual, but with no explanation of why it should work that way. [4]
I would be interested in any explanations of why it might be intended
behaviour, or ways in which people might be relying on the current
behaviour.
A proposal to change the behaviour was included in a wider RFC about
standardising increment and decrement behaviour, but it never got beyond
draft status. [5] I would prefer not to reopen that wider debate, but
focus on this single issue.
As far as I can see, the change would be to add a "case IS_NULL" branch
to decrement_function in zend_operators.c to match the one in
increment_function. [6]
I will happily write up an RFC to formalise this, but wanted to gather
people's immediate thoughts first.
Links:
[1] https://bugs.php.net/bug.php?id=20548
[2] https://bugs.php.net/bug.php?id=25674
[3] https://bugs.php.net/bug.php?id=41690
[4] https://www.php.net/manual/en/language.operators.increment.php
[5] https://wiki.php.net/rfc/normalize_inc_dec
[6]
https://php-lxr.adamharvey.name/source/xref/master/Zend/zend_operators.c#2359
Regards,
--
Rowan Tommins (né Collins)
[IMSoP]
--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: http://www.php.net/unsub.php
