Bug #65485 [Opn->Nab]: Cast gives different values in one way or the other

Edit report at https://bugs.php.net/bug.php?id=65485&edit=1 ID: 65485 Updated by: johannes@php.net Reported by: stephane at it-asia dot com Summary: Cast gives different values in one way or the other -Status: Open +Status: Not a bug Type: Bug Package: *General Issues Operating System: Windows 8 & Mint Maya PHP Version: 5.4.18 Block user comment: N Private report: N New Comment: 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. Casting to string will be imprecise, then doing cast to int will be imprecise again. Two imprecisions increase the difference. Previous Comments: ------------------------------------------------------------------------ [2013-08-20 08:50:20] stephane at it-asia dot com Description: ------------ I have different value when I cast a double to int and when I cast to string before casting to int. I understand 39.48 is difficult to store in base 2. The problem is the cast algorythm is not the same if you cast a float to int or if you cast a float to string, This involves huges mistakes in accountancy software. Whatever the way you choose (float -> int or float -> string -> int ) , you should have the same result at the end. Please define the right way to process data in that case. I have the same problem with almost every machines, Windows or Debian based. Thanks ! Test script: --------------- $d = "39.48" * "100"; print("39.48 * 100 : "); var_dump ($d); $i = (int) $d; print("<br />int: "); var_dump ($i); $s = (string) $d; print("<br />string: "); var_dump ($s); $i = (int) $s; print("<br />int: "); var_dump ($i); Expected result: ---------------- same value if you cast double => int and if you cast double => string => int Actual result: -------------- 39.48 * 100 : double(3948) int: int(3947) string: string(4) "3948" int: int(3948) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=65485&edit=1