PHP Rounding Float Values With Ceil And Result Comparison Is Not As It Must Be

Question

I have a PHP function as

function func(){

    function round_up($value, $decPlaces) {
        return ceil($value * pow(10, $decPlaces)) / pow(10, $decPlaces);
    }

    $a=21.31;
    $b=2;
    $c=10.64;
    $d=0.03;

    $xxx=$a;
    $yyy=round_up($b*$c,2)+round_up($d,2);
    $zzz=($xxx===$yyy);

    var_dump($xxx,$yyy,$zzz);
}

This function outputs

float(21.31) float(21.31) bool(false)

It seems xxx equal to yyy but why zzz is false? Where is the problem in this function and result?

See: http://floating-point-gui.de/errors/comparison – KIKO Software Feb 02 '18 at 23:38 — KIKO Software, Feb 02 '18 at 23:38

MariuszT · Accepted Answer · 2018-02-02T23:52:40.093

2

Just change last line to this to see difference:

var_dump(number_format($xxx, 20), number_format($yyy, 20), $zzz);

Here are some helpful info about the problem:

https://stackoverflow.com/a/3148991/4180451 https://secure.php.net/manual/en/language.types.float.php
https://andy-carter.com/blog/don-t-trust-php-floating-point-numbers-when-equating

and many more... :)

edited Feb 02 '18 at 23:52

answered Feb 02 '18 at 23:45

MariuszT

59
4

1

Thank you so much for your gold answer. This information is very important for financial operations as money or etc. – MERT DOĞAN Feb 02 '18 at 23:58

PHP Rounding Float Values With Ceil And Result Comparison Is Not As It Must Be

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