Terrible, terrible, behaviour but there are lots of similar examples in PHP because it evolved over time rather than being designed as-is. Some of these things are being fixed over time, like this very example, others can't/won't be.

So true.

One I ran into recently was comparing hashes that start with '0e' and contain only a numeric component after that prefix. Failure to use the identity operator means that you can have two different hashes returning... equality. PHP apparently thought it a good idea to coerce that into 0 raised to an exponent, which of course always yields zero. e.g.:

    php > var_dump('0e41235843934' == '0e61193475532');
    bool(true)

But it's also not outside the realm of possibility that someone won't eventually forget to add an extra '=' and induce a very difficult bug to isolate...

Noticed "0.2" == "0.20" as another example

[1] https://www.php.net/manual/en/language.operators.comparison.... [2] https://www.php.net/manual/en/language.types.type-juggling.p...

I don't know. It's one of those cases where fixing it to do the "right" thing would potentially break a lot of software depending on this sort of erroneous behavior. Part of me wants to say "I hope so" and part of me is kinda terrified at what might happen if they did. Shouldn't be difficult to fix, but it would definitely take some time.

Someone should know if there's a decent linter that would pick this up to make it easier to fix, I would imagine!

> I did not think this was possible as there is no type coercion and not well documented.

I think when applying the equality operator (==) in lieu of the identity operator (===) between strings PHP uses heuristics to decide what to do. If it looks like a number, it coerces it into an int or a float. As an example:

    php > var_dump('1e12' == 1e12);
    bool(true)

It is well documented that when converted to integers, strings containing a number at the start will be converted to that number, and drop any string after, e.g. '1eabc' becomes 1.

It's also been a best practice for a looong time (since something like PHP 5.4) to use === to test for equality.

Yes, it's documented, but it doesn't make it any less obnoxious. IMO the thought of implicit conversion is absolutely asinine.

But, in fairness, PHP isn't the only language that does this. Python, at least, is more sane.

> and drop any string after, e.g. '1eabc' becomes 1.

In defense of PHP, it does yield a NOTICE if you attempt to apply certain operations to implicitly cast strings (e.g. addition), so there's that.

Suffices to say that while I've written PHP for years, I'm quite comfortable with its idiosyncrasies, it doesn't mean I don't find them appallingly brain damaged. :)

FWIW the identity operator (===) is also a best practice in JS for nearly identical reasons which also exhibits similar (and in some cases nearly identical) implicit casting.

So true.

I can't really complain. Well, I can, and that's what I've been doing in much of this thread.

It's mostly just yelling at the sky for no good reason other than to make myself feel better at this point, if I were to be completely honest with you.

The problem for me is working with a big legacy codebase. I'd rather have php break backwards compatibility and change === to ==.

Nope.

I wish I were kidding. This is where PHP diverges from JS in a way that really will surprise people coming from JS (PHP7.something):

    php > var_dump("0.2" == "0.20");
    bool(true)

I have mixed feelings on this.

On the one hand, I desperately want to agree with you, and probably for all the same reasons. On the other hand, languages like PHP with their dynamic typing system make implicit conversion almost a necessity to retain the identity operator (===) because they strive not to break "too much" (for some value of "too much").

Although, I'd imagine your argument is akin to "well, just cast it to what you expect" (e.g. `(int)$_GET['value']`), and you're right. That's how it should be done, of course.

But, as you mentioned about legacy code bases... sometimes it's not that easy.

[0] https://www.php.net/manual/en/migration80.php

No, Perl is completely different and IMO it's the only mainstream dynamically typed language that has sane comparison operators.

Perl has two sets of operators, numeric (==, +, *, <, >, <=> etc.) and stringwise (eq, ., lt, gt, cmp etc.). You can think of them as explicit (but concise) casts. For example, Perl's $foo eq $bar is roughly equivalent to Python's str(foo) == str(bar).

It is true that "foobar" == 0 returns true in Perl but, as I showed above, it does that for a completely different reason.

And it also just makes sense from the language design perspective to fix that behaviour. Having a major version coming is a good time to fix such stuff imho.

=== is strict.

There is no way to disable the `==` operator or make it do strict comparisons (yet)

    declare(scrict_types=1);

Php has good documentation with examples which I appreciate :

https://www.php.net/manual/en/language.operators.comparison....

As to why that is, perhaps someone with more Perl knowledge can chime in. I suspect it has to do with undef being inconvenient for signalling failure, since its evaluation will be context dependent (an array of undef is true but a numeric undef is false).

Type conversion is built into the language at a fundamental level. Languages that borrows the syntax but not the type model can be confusing in cases, but Perl is pretty consistent once you get the basics.