On 13/06/13 08:59, BUSCHKE Daniel wrote:
Hi all,
I want to start a discussion about a PHP behaviour that drives me crazy for
years. For the beginning I would like you to guess what the result of the
following snippet will be:
var_dump('PHP' == 0);
I know the difference of == and === but the result was unexcpected for me. And I hope it
is also for you. The result is simply "true". Why is it true? I guess this
happens because of the conversion from 'PHP' to a number which will be 0 in PHP. And of
course 0 equals 0. There are several points that I just want to drop into this
mailinglist to discuss about:
1. Why? :)
42
2. Why is PHP converting the String into a Number instead of converting the
Number into a String? (If my guess concerning the behaviour is correct)
Since PHP is a weakly-typed language, it has to choose one way or the
other. The behaviour *is* predictable if you know what the rule is (I'm
sure the order of conversion is documented somewhere).
3. Why is PHP throwing data away which has the developer explicit given to the
interpreter?
Because PHP is weakly-typed, the developer is not being sufficiently
explicit. Try
php -r 'var_dump(intval('PHP') == 0);'
and
php -r 'var_dump('PHP' == strval(0));'
to see explicit code. Anything less is implicit.
4. Why does var_dump(0 == 'PHP'); has the same result as the snippet above?
This meens that the equal operator is not explictly implemented in the string
or integer?
The rule is consistent: it always converts the string to an integer
whatever the order.
5. Thats a bug I have opend: https://bugs.php.net/bug.php?id=51739 where I also had the same
problems because "8315e839da08e2a7afe6dd12ec58245d" was converted into float(INF) by
throwing everything starting from "da08.." away.
That's a very different proposition, and probably has more to do with
word size: float is 32-bit, so only the first 32 bits are used and if
anything else is found the conversion falls back to INF. To handle
really big integers like 8315e839da08e2a7afe6dd12ec58245d you probably
need a more specialist library (or language)
I am using PHP since the year 2000. This means I have 13 years of experience in PHP and I really
would like you to NOT just answer "works as designed". I know it works as designed but I
want to discuss the design. Also I know that the "fuzzy" behaviour of type conversion is
a main feature of PHP. I guess this is one point which makes PHP that successfull. But - in my
opinion - the described behaviour is to fuzzy and just confuses developers.
The weak typing *is* a feature of PHP: other languages are more suitable
when you need more enforcement of types: Java, for example.
With all due respect to an experience programmer, years of experience do
not make up for a limited tool set.
Best Regards
Daniel Buschke
Cheers
Pete
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
