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Date: Tue, 26 Feb 2019 13:27:23 +0100
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To: PHP internals <internals@lists.php.net>
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Subject: [RFC] Saner string to number comparisons
From: nikita.ppv@gmail.com (Nikita Popov)

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Hi internals,

I think it is well known that == in PHP is a pretty big footgun. It doesn't
have to be. I think that type juggling comparisons in a language like PHP
have some merit, it's just that the particular semantics of == in PHP make
it so dangerous. The biggest WTF factor is probably that 0 == "foobar"
returns true.

I'd like to bring forward an RFC for PHP 8 to change the semantics of ==
and other non-strict comparisons, when used between a number and a string:

https://wiki.php.net/rfc/string_to_number_comparison

The tl;dr is that if you compare a number and a numeric string, they'll be
compared as numbers. Otherwise, the number is converted into a string and
they'll be compared as strings.

This is a very significant change -- not so much because the actual BC
breakage is expected to be particularly large, but because it is a silent
change in core language semantics, which makes it hard to determine whether
or not code is affected by the change. There are things we can do about
this, for example the RFC suggests that we might want to have a transition
mode where we perform the comparison using both the old and the new
semantics and warn if the result differs.

I think we should give serious consideration to making such a change. I'd
be interested to hear whether other people think this is worthwhile, and
how we could go about doing it, while minimizing breakage.

Regards,
Nikita

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