Bug #62465 [Com]: intval of floats

Edit report at https://bugs.php.net/bug.php?id=62465&edit=1 ID: 62465 Comment by: fabrizio at queensboro dot com Reported by: fabrizio at queensboro dot com Summary: intval of floats Status: Not a bug Type: Bug Package: *General Issues Operating System: FreeBSD 9.0-RELEASE - amd64 PHP Version: 5.4.4 Block user comment: N Private report: N New Comment: Wouldn't make sense to have the conversion to INT work based on the precision ? precision32: - intval(float(894.99999999999988631316227838397)) = 894 precision 14: - intval(float(894.99999999999988631316227838397)) = 895 Previous Comments: ------------------------------------------------------------------------ [2012-07-02 18:54:38] fabrizio at queensboro dot com I never stop learning!! Thank you very much ! ------------------------------------------------------------------------ [2012-07-02 18:48:14] rasmus@php.net Well, that is just because your output precision is set low enough so when the value is printed it prints as 895. Try adding this to the top of your test script: ini_set('precision',32); And no, this isn't a modern language vs. old language thing. For example, in Python: Python 2.7.3 (default, Apr 20 2012, 22:39:59) >>> a=8.9500 >>> print a*100 895.0 >>> from math import floor >>> print floor(a*100) 894.0 The way to fix this is to use arbitrary precision math routines and every scripting language, including PHP (see gmp, bcmath) provides those, but they are so much slower than the cpu-provided floating routines that it is hard to justify. ------------------------------------------------------------------------ [2012-07-02 18:23:53] fabrizio at queensboro dot com correct misspelled OS ------------------------------------------------------------------------ [2012-07-02 18:23:01] fabrizio at queensboro dot com Very interesting. Thank you for your link, I always assumed that this was an issue for old languages and that new ones would have corrected the conversion to integer using some sort of checking against the "to_string" (I am saying this without knowing what it takes or what the code looks like). As you can see here, the code knows that the value is a float(895), without decimals, so the integer should be the same, else I would expect an output like float(894.99999999...) during the var_dump. <?php $grand_total = '8.9500'; var_dump( $grand_total, $grand_total*100, round($grand_total*100), intval($grand_total*100) ); ?> string(6) "8.9500" float(895) float(895) int(894) ------------------------------------------------------------------------ [2012-07-02 16:47:24] rasmus@php.net Floating point values have a limited precision. Hence a value might not have the same string representation after any processing. That also includes writing a floating point value in your script and directly printing it without any mathematical operations. If you would like to know more about "floats" and what IEEE 754 is, read this: http://www.floating-point-gui.de/ Thank you for your interest in PHP. You are going to want to round() and not truncate here. ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at https://bugs.php.net/bug.php?id=62465 -- Edit this bug report at https://bugs.php.net/bug.php?id=62465&edit=1