Bug #70447 [Nab]: Wrong float rounding using round function

Edit report at https://bugs.php.net/bug.php?id=70447&edit=1 ID: 70447 User updated by: m dot mochetti at design-it dot de Reported by: m dot mochetti at design-it dot de Summary: Wrong float rounding using round function Status: Not a bug Type: Bug Package: *General Issues Operating System: Linux (ubuntu) PHP Version: 5.5.29 Block user comment: N Private report: N New Comment: Ok, so added the following line of code: $cents = round(round($cents,3), 2); And works fine. Thanks. Previous Comments: ------------------------------------------------------------------------ [2015-09-07 11:23:18] requinix@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. <?php ini_set("precision", 20); $float = 87.755; $units = (int)floor($float); $cents = (float)($float - $units); var_dump($cents); ?> float(0.75499999999999545253) (that was with PHP x86 on Windows) Round to three decimal places first, as that is the value you expected to be working with. Then round it to two decimal places. ------------------------------------------------------------------------ [2015-09-07 11:14:25] m dot mochetti at design-it dot de Description: ------------ I'm having a serious issue regarding prices not being properly rounded in a sales platform the company I work for is currently developing. Please take a look at the Test script attached, it showcases the issue. Test script: --------------- <?php $float = 87.755; $units = (int)floor($float); $cents = (float)($float - $units); echo "UNITS = ".$units; // UNITS = 87 echo "<br>"; echo "CENTS = ".$cents; // CENTS = 0.755 echo "<br>"; echo "ROUNDED CENTS = ".round($cents, 2); // ROUNDED CENTS = 0.75 --> WRONG!! echo "<br>"; echo "ROUNDED CENTS (without using variable): ".round(0.755, 2); // ROUNDED CENTS (without var) : 0.76 --> CORRECT!! ?> Expected result: ---------------- round(0.755, 2) should return the same result as round($var, 2) // being $var a calculated value that ended up to be 0.755 Actual result: -------------- round(0.755,2) = 0.76 round($var, 2) = 0.75 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=70447&edit=1