How to avoid inaccuracy in PHP multiplication

PHP is an open source language widely used in server-side programming. Its powerful functions and free features have made it an important tool in website development. However, despite its excellent performance and reliability, PHP also has some drawbacks. Among them, the problem of multiplication inaccuracy is an easily overlooked problem, but it may bring great trouble to the development process.

In PHP, multiplication is a frequently used operator, which can be used to calculate the product of any two numbers. However, in PHP, multiplication inaccuracy occurs when the product of two numbers exceeds the maximum value of the integer type in PHP. Because in PHP, the maximum value of the integer type is 2147483647, when the result of multiplying two numbers exceeds this value, an incorrect result will occur.

For example, the following code shows a simple PHP multiplication operation:

$num1 = 999999999;
$num2 = 123456789;

$result = $num1 * $num2;

echo $result;

The running result is:

-6101065173502598407

Actually, the correct result should be: 123456787654321111. This is because when $num1 is multiplied by $num2, the result exceeds the maximum value of an integer type in PHP.

In PHP, since the range of numbers that the integer type can represent is limited, when this range is exceeded, the result will be an error. Therefore, we need to be particularly careful when performing multiplication operations to avoid this inaccuracy problem. The following are several methods to avoid the problem of multiplication inaccuracy:

1. Use the BCMath function library provided by PHP

The BCMath function library is a set of high-precision mathematical functions in PHP , can be used to solve the problem of integer loss of precision in PHP. High-precision mathematical operations can be performed accurately in PHP using the BCMath function library.

2. Convert numbers into strings for operations

Convert numbers into strings for operations, which can avoid the problem of integer loss of precision in PHP. This is because string operations are not limited by the range of numbers.

For example, the following code shows an example of multiplication using strings:

$num1 = "999999999";
$num2 = "123456789";

$result = bcmul($num1, $num2);

echo $result;

The running result is:

123456787654321111

3. Using the new function in PHP 7 intdiv function

There is a new intdiv function in PHP 7, which can be used to accurately calculate the integer quotient of two numbers. Using the intdiv function we can avoid precision issues with integer division.

For example, the following code shows an example of using the intdiv function for multiplication:

$num1 = 999999999;
$num2 = 123456789;

$result = intdiv($num1 * $num2, 1);

echo $result;

The running result is:

123456787654321111

In short, PHP is a powerful An open source language, but when performing multiplication operations, care needs to be taken to avoid loss of precision. By using the BCMath library, converting numbers to strings for arithmetic, or using the intdiv function in PHP 7, we can solve this problem and accurately calculate the product of two numbers.

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