Bug #15164 Updated: can php do a substraction? ;)

ID: 15164 Comment by: mik@x.org.pl Reported By: mik@x.org.pl Status: Bogus Bug Type: Math related Operating System: linux 2.2.19 PHP Version: 4.1.1 New Comment: thanks very much for explaining. i haven't link teory with practice (about floats). probably i realy work too much. :) let me ask one more question: if i store prices in postgresql as numeric(10,2), how can i secure handle it in php? could i do: $price_c = (int)($psql_num_price * 100); //? and how to write it back? $psql_num_price = $price_c / 100; //? thanks one more time. Previous Comments: ------------------------------------------------------------------------ [2002-01-22 11:13:14] hholzgra@php.net lets call it what it is: an inevitable rounding error that occurs when converting floating point values from internal binary to human readable decimal format use integers and count cents instead of dolars or use http://php.net/number_format for output as already suggested by the way: the result is 56.999999..., not 57.999999..., so you are off by 0.000.....1 not 0.99999..... which is not so bad after all ------------------------------------------------------------------------ [2002-01-22 11:02:04] mik@x.org.pl what type should i do for currencies, so? ok. let's don't call it a bug... let's call it for example a little magic of floats. but don't u think u could correct it? ------------------------------------------------------------------------ [2002-01-22 10:29:10] jan@php.net floats are not supposed to be exact (per definition). do not use them on currencies. calculate cents ant use (agein) number_format() to display them prooperly. No bug in PHP, bogus. ------------------------------------------------------------------------ [2002-01-22 09:17:32] mik@x.org.pl my previous bug report was 15162. i wrote about (int) cast there. another bug may be a reason of that. i do: (267.57 - 267) * 100 and i get: 57.999999999999 (i expected 57) [may be i work too much...] consider this: <? $price = 267.57; $price_dolars = floor($price); echo "number of cents is: " . ($price - $price_dolars)*100 . "<BR>"; ?> ------------------------------------------------------------------------ Edit this bug report at http://bugs.php.net/?id=15164&edit=1