PHP 8.1.15 Released!

pow

(PHP 4, PHP 5, PHP 7, PHP 8)

pow指数表达式

说明

pow(mixed $num, mixed $exponent): int|float|object

返回 numexponent 次方的幂。

注意:

可以使用 ** 运算符代替。

参数

num

底数

exponent

指数

返回值

numexponent 次方。如果两个参数都是非负整数且结果可以用整数表示,则返回 int 类型,否则返回 float

范例

示例 #1 pow() 的一些例子

<?php

var_dump
(pow(2, 8)); // int(256)
echo pow(-1, 20); // 1
echo pow(0, 0); // 1
echo pow(10, -1); // 0.1

echo pow(-1, 5.5); // NAN
?>

注释

注意:

本函数会转换所有输入为数字,甚至是非标量值,将会导致怪异的结果。

参见

add a note

User Contributed Notes 6 notes

up
49
chris at ocportal dot com
10 years ago
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.
up
17
raiika
4 years ago
It is official now that you could use

<?php

2
** 3; // 8

// instead of

pow(2, 3); // 8

?>
up
11
gilthansREMOVEME at gmail dot com
16 years ago
Note that pow(0, 0) equals to 1 although mathematically this is undefined.
up
2
Roman
2 years ago
If you use negative numbers, you need to use brackets for using with **

<?php

-1 ** 2; // -1

(-1) ** 2; // 1

?>
up
-1
scott at arciszewski dot me
8 years ago
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.

<?php
// These two will be equivalent as of PHP 5.6.0
$x = $y ** 2;
$x = pow($y, 2);
?>
up
-6
jaxx1rr at gmail dot com
3 years ago
funny thing

number_format(pow(2, 1023));
gives a long number

but number_format(pow(2, 1024));
gives inf
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