Re: Is php safe for e-commerce applications?

Would sprintf() handle your needs? This seems to work correctly... $val = sprintf("%.0f",(10*(8.20-0.20))); produces a string $val equal to 80. Is this too geeky? Jimtronic

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! Hellllllpppppppp...... George -- PHP General Mailing List (http://www.php.net/) To unsubscribe, e-mail: php-general-unsubscribe@lists.php.net For additional commands, e-mail: php-general-help@lists.php.net To contact the list administrators, e-mail: php-list-admin@lists.php.net

-- Jim Musil --------- Multimedia Programmer Nettmedia ------------- 212-629-0004 jim@nettmedia.com