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phpnumberscomparisonroundingvar-dump

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

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?

Solution

  • 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... :)