PHP's BC Math series Mathematical functions

First, frequently asked questions

When using PHP for computing, you often encounter the problem of precision, the following two common examples:

1. Comparison of operations

The result of the following expression output is not 相等 :

<?php echo 2.01 - 0.01 == 2 ? ‘相等‘ : ‘不相等‘;  // 不相等

2. Type conversion

The result of the following expression output is not 201 (if you want to output the result you want, you need to go to the string and then to int):

<?php$num = intval(2.01 * 100);var_dump($num);    // int(200)

You may find it strange, however, that this is not a PHP bug, if you want to learn more about the two articles that you can refer to Brother Bird:

1. About PHP floating-point numbers you should know (all ' bogus ' about the float in PHP)
2. A FAQ for PHP floating-point numbers

Second, BC MATH

The BC Math series mathematical functions provided with PHP can solve the problem above. For mathematical calculations of arbitrary precision, BC Math provides a binary calculation of numbers that support any size and precision represented by a string, up to 2147483647-1 (or 0x7fffffff-1).

Use the functions provided by BC MATH to solve the above problem.

1. Comparison of operations

bccomp-compare two arbitrary-precision numbers:

<?php$num = bccomp(2.01 - 0.01, 2, 2);   var_dump($num); // int(0)

Note: If two number equals returns 0, the left number compares to the number on the right to return 1, otherwise returns-1.

2. Type conversion

Bcmul-2 an arbitrary-precision numerical multiplication calculation:

<?php$num = bcmul(2.01, 100, 0);var_dump($num);    // string(3) "201"var_dump(intval($num));    // int(201)

Note: Returns the result as a string type

Using the BC Math series math functions allows us to reduce errors, avoid unnecessary errors, and to see the details of parameters and the use of other functions, please refer to the official PHP documentation: http://php.net/manual/zh/book.bc.php

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PHP's BC Math series Mathematical functions