pow()

(PHP 4, PHP 5, PHP 7)

指数表达式

说明

返回$base的$exp次方的幂。如果可能，本函数会返回integer。

参数

The base to use

指数

返回值

$base的$exp次方的幂。 If both arguments are non-negative integers and the result can be represented as an integer, the result will be returned withintegertype, otherwise it will be returned as afloat.

更新日志

范例

Example #1pow()的一些例子

注释

本函数会转换所有输入为数字，即使是非标量值，会导致怪异的（weird）结果。

参见

• exp() 计算 e 的指数
• sqrt() 平方根
• bcpow() 任意精度数字的乘方
• gmp_pow()Raise number into power

Many notations use "^" as a power operator, but in PHP (and other C-based languages) that is actually the XOR operator. You need to use this 'pow' function, there is no power operator.
i.e. 3^2 means "3 XOR 2" not "3 squared".
It is particular confusing as when doing Pythagoras theorem in a 'closet points' algorithm using "^" you get results that look vaguely correct but with an error.

Note that pow(0, 0) equals to 1 although mathematically this is undefined.

It is official now that you could use 

As of PHP 5.6.0alpha2, there is now an exponentiation operator. If this is kept in the final release, it may be worth noting here. 

funny thing
number_format(pow(2, 1023));
gives a long number
but number_format(pow(2, 1024));
gives inf

鹏仔微信 15129739599 鹏仔QQ344225443 鹏仔前端 pjxi.com 共享博客 sharedbk.com