Reading the Bug report, it was mentioned if you want precision
mathmatics, use BCMath
http://www.php.net/manual/en/ref.bc.php
That will give you the precision you are looking for.
Jason Lotito
[EMAIL PROTECTED]
www.NewbieNetwork.net
> -Original Message-
> From: George Whiffen [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, December 05, 2001 3:05 PM
> To: [EMAIL PROTECTED]
> Subject: [PHP] Is php safe for e-commerce applications?
>
>
> What a scary day, and it just gets worse
>
> 1. A user finds their account balance is displayed
> incorrectly on one of my live e-commerce sites.
>
> 2. I discover that "floor()" intermittently gives the wrong
> answer i.e.
>
> print floor(10*(8.20 - 0.20));
> Answer : 79
>
> print floor(10*(8.10 - 0.10));
> Answer : 80
>
> (php 4.0.6 and 4.0.4.pl1 under Linux 2.2.19.)
>
> 3. I find this is a known "feature" with no intention of ever
> being fixed. See http://bugs.php.net/bug.php?id=6220
>
> print floor( (0.7 + 0.1) * 10);
> Answer : 7
>
>
> 4. I check the php documentation that was added because of that bug
> (http://www.php.net/manual/en/language.types.float.php) and
> discover :-
>
> "never trust floating number results to the last digit and
> never compare floating point numbers for equality."
>
> 5. I realise that the "last digit" might also be the first so
> that means never trust anything except integers!
>
> 6. The truth really sinks in... It seems I simply cannot use
> php for e-commerce applications unless I convert all money to
> integers e.g. $4.32 must be handled as 432 cents, or all
> arithmetic operations and comparisons have to be converted to
> use bc functions. Instead of :
>
> if ($cost == 10.00)
> you must write
> if (bcomp($cost,10.00,2)) == 0)
> etc.,etc.
>
> 7. The horror unfolds... php is just as full of geeko-trash
> as C/Perl/Java and the rest of them! I will have to spend the
> rest of my life worrying about types/casts/floating point
> precision and all that garbage even when I'm just adding up
> dollars and cents! I can't even escape to Italy and work in
> Lira, they're switching to euros with decimal places too! I
> should have stayed with Java, it may be rubbish but at least
> it's obviously rubbish!
>
>
> Please someone, tell me I'm wrong!
>
> Tell me that 0.1 + 0.7 can be 0.8 and not almost 0.8!
> Tell me I don't have to check the last three years of work!
> Tell me php isn't just for kids waiting to graduate/degradate
> to Java! Tell me the techno-geeks haven't won!
>
> Hell..
>
>
> George
>
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