Causes and avoidance strategies of PHP floating point calculation errors

PHP, as a popular server-side scripting language, often encounters problems with loss of precision or calculation errors when performing floating-point calculations. These problems may affect the accuracy of the program. and stability. This article will explore the causes of PHP floating point calculation errors, propose some avoidance strategies, and give specific code examples for reference.

1. Reasons for PHP floating point calculation errors

In computers, floating point numbers are represented in binary form, and binary cannot accurately represent all decimal decimals, which leads to Floating point precision issues. In addition, there are rounding errors and truncation errors in floating-point number operations. These errors gradually accumulate during the calculation process, eventually leading to inaccuracy in the calculation results.

In PHP, you need to pay special attention when using floating point calculations. Some seemingly simple calculations may also produce errors. For example:

$num1 = 0.1;
$num2 = 0.2;
$sum = $num1 + $num2;
echo $sum; // 结果并非0.3，而是一个接近0.3的近似值

This seemingly simple addition calculation may cause errors, so you should always be wary of this happening in actual coding.

2. Strategies to avoid floating point calculation errors in PHP

2.1 Use integers for calculation

In order to avoid floating point calculation errors, a common strategy is to convert floating point numbers to Perform calculations on integers and finally convert the results back to floating point numbers. This reduces the possibility of loss of accuracy.

$num1 = 0.1;
$num2 = 0.2;
$sum = intval($num1 * 100) + intval($num2 * 100) / 100;
echo $sum; // 输出0.3

2.2 Use specific functions to process floating point numbers

PHP provides some functions to process floating point numbers, such as bcadd(), bcsub() , bcmul() and bcdiv() and other functions, these functions can perform floating point calculations more accurately.

$num1 = '0.1';
$num2 = '0.2';
$sum = bcadd($num1, $num2, 1);
echo $sum; // 输出0.3

2.3 Use error range when comparing floating point numbers

When comparing two floating point numbers to see if they are equal, you should use an error range for comparison instead of using ==# directly ##operator to compare.

$num1 = 0.1 + 0.2;
$num2 = 0.3;
if (abs($num1 - $num2) < 0.0001) {
    echo '相等';
} else {
    echo '不相等';
}

The above is the detailed content of Causes and avoidance strategies of PHP floating point calculation errors. For more information, please follow other related articles on the PHP Chinese website!