Reasons for PHP floating point calculation errors

Example:(Recommended learning:PHP video tutorial)

echo intval(0.58*100);//结果为57 echo intval((0.1 + 0.7) * 10);//结果为7

The reason for this is that the computer Some floating-point numbers cannot be accurately represented internally in binary, just like we cannot accurately represent 10/3 in decimal.

The internal representation of floating-point numbers in the computer: IEEE 754. If you don’t understand, look it up yourself Information

You can also refer to this article by Bird Brother: http://www.laruence.com/2013/03/26/2884.html

'; echo intval(bcmul(0.58, 100));//58 echo '
'; echo floor(strval(0.58*100));//58 echo '
'; echo (int)(0.58 * 1000/10);//58 echo '
'; echo intval((0.1 + 0.7) * 10);//7,注意啦 echo '
'; echo intval(bcadd("0.1", "0.7",1) * 10); //8 ?>

Let’s look at another example

'; $a = 0.1 + 0.7; echo $a; //0.8 echo '
'; if($a == 0.8){ echo '一天一小步'; }else{ echo '一年一大步'; //这里输出 } echo '
'; if(strval($a) == 0.8){ echo '一天一小步'; //这里输出 }else{ echo '一年一大步'; } echo '
'; if(bcadd(0.1, 0.7,1) == 0.8){ echo '一天一小步'; //这里输出 }else{ echo '一年一大步'; } /* 结果: 不相等 0.8 一年一大步 一天一小步 一天一小步 */ ?>

$a = 0.00...00(n zeros)1 0.7; When using strval to obtain the value of $a, the result of whether $a and 0.8 are equal will be caused by the different number of n zeros. Different

The bcadd function will add 2 numbers, depending on how many decimals you choose to keep and discard the following decimals

Look at a division example:

'; echo intval(160500643816367088/10);//16050064381636710 echo '
'; echo bcdiv(160500643816367088,10);//16050064381636708 ?>

So for sensitive data such as floating point numbers to calculate amounts, it is recommended to use PHP's BC function

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