意外的PHP数学小数运算

Question

    $nt=(float) number_format("26031.87",2,".",""); // 26031.87
    $nt2=(float) 546669.02-520637.15; // 26031.87

    if($nt>$nt2)
     echo "$nt / $nt2 ⇽ What's wrong with this!? :@";

the point is why this happen?, if visually looks the same, a chunky solution is doing number_format() to $nt2, but... WHY??

updating :: $nt-$nt2 outputs 3.6379788070917E-12

Answer 1

http://php.net/manual/en/language.types.float.php see that big red warning banner. :)

For comparing floats you can use:

if (abs($nt1-$nt2) < 0.00001) {
    echo "Equal!";
}

(change 0.00001 to comparison precision you need).