ID: 45970 Updated by: [EMAIL PROTECTED] Reported By: jan dot vernieuwe at webline dot be Status: Bogus Bug Type: Math related Operating System: FreeBSD PHP Version: 5.2.6 New Comment:
Oh, Scott just beat me. :-) Well here's a bit extra I wrote: The result of subtraction ($myVal) is stored as a value slightly less than 57.645, due to floating-point precision, which is why it rounds to 57.64 in the 3rd var_dump(). The 2nd and 4th var_dump() are using the same value, with closer float representation to what you want (57.645). By that I mean, in the 4th, as a string, $myVal is first converted to a string, exactly as the first example does to print the var_dump() output, then that "57.645" string is converted to float, exactly as the numeric version in the 2nd example is when the script is parsed/compiled (so they have the same internal float representation, and will behave the same). Previous Comments: ------------------------------------------------------------------------ [2008-09-02 09:28:07] [EMAIL PROTECTED] 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://docs.sun.com/source/806-3568/ncg_goldberg.html Thank you for your interest in PHP. ------------------------------------------------------------------------ [2008-09-02 09:08:36] jan dot vernieuwe at webline dot be Description: ------------ Rounding a calculated float gives bad results, rounding it as a string works as intended. Reproduce code: --------------- <?php echo "<pre>"; $total = 332.145; $substract = 274.5; $myVal = $total-$substract; var_dump($myVal); var_dump(round(57.645,2)); var_dump(round($myVal,2)); var_dump(round("$myVal",2)); echo "</pre>"; ?> Expected result: ---------------- float(57.645) float(57.65) float(57.65) float(57.65) Actual result: -------------- float(57.645) float(57.65) float(57.64) float(57.65) ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=45970&edit=1
