php计算给出了1500000-20％的奇怪结果

Question

May be I might be blind or silly, but look at my function:

function max_min_twenty($value) {
if ((int)$value == 0) {
    return "0"; 
} else {
    $percent_val = ((int)$value / 100) * 20;
    $maxvalue = (int)$value + $percent_val;
    $minvalue = (int)$value - $percent_val;
    $returnvalue = round($minvalue)."-".round($maxvalue);
    return $returnvalue;
}
}

Seems that this is really easy! It works like it should, but if my $value is 1500000 it gives me back 1,2E+6 for $minvalue - It does well if I choose a different number or if I change the percent to 19 or 21. Whats that?

Its running on PHP Version 5.2.4-2ubuntu5.27

Answer 1

Format the number explicitly as an integer? round returns a float and so I believe the default formatting is "getting confused" or "hitting an edge case" and reverts to displaying scientific notation. (I can't trigger the problem on ideone - it might be specific to a particular PHP version/environment - but the symptoms fit.)

Try sprintf:

return sprintf("%d-%d", $minvalue, $maxvalue);

(I removed round as the %d forces the arguments to be treated as integers; however, there might be subtle differences in the rounding rules .. I don't know.)