This will add support for decrementing alphanumeric strings (“ab”, for example) to complement the existing incrementing behaviour.
At present, incrementing alphanumeric strings is supported. For example:
$x = "z"; $x++; // $x is now "aa"
However, decrementing alphanumeric strings is not:
$x = "z"; $x--; // $x is still "z"
Under this proposal, alphanumeric strings would be decrementable:
$x = "z"; $x--; // $x is now "y"
It would also handle the edge case of decrementing from “a”, choosing to result in 0 (this may be subject to change):
$x = "a"; $x--; // $x is now 0
The patch at present additionally changes how empty strings are incremented. At present, it works as follows:
$x = ""; $x++; // $x is now "1" (string) $x = ""; $x--; // $x is now -1 (int)
With this patch, it is now consistent:
$x = ""; $x--; // $x is now "-1" (string)
This might arguably be a BC break, as now decrementing for these strings would work, while existing code might assume that doesn't work. I doubt there is any code relying on that though, especially since “a”++ is a relatively obscure feature.
Next PHP 5.x. Failing that, next PHP x.
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How should decrementing “a” be handled? The patch and behaviour as proposed decrement to 0, however possibly not decrementing and emitting a warning might make more sense.
Does not affect $x += 1 and $x -= 1, nor $x = $x + 1 and $x = $x - 1, as both of these do not support alphanumeric increment at present.
In future, alphanumeric increment being supported $x += 1 and $x = $x + 1 might be desirable, but that is not within the scope of this RFC.
Merge into PHP 5.6? (Will assume this requires 2/3 majority, due to new language feature)
Voting started 2014-01-21 and ended 2014-01-28.
https://github.com/php/php-src/pull/546
Considered final patch, unless bugs are found.
Not merged in at present.
Mailing list discussion: http://marc.info/?l=php-internals&m=138687859827708&w=1
None as yet?