(PHP 4, PHP 5, PHP 7, PHP 8)
pow — 指数表达式
num底数
exponent指数
num 的 exponent
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。
示例 #1 pow() 的一些示例
<?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。
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.It is official now that you could use
<?php
2 ** 3; // 8
// instead of
pow(2, 3); // 8
?>Note that pow(0, 0) equals to 1 although mathematically this is undefined.If you use negative numbers, you need to use brackets for using with **
<?php
-1 ** 2; // -1
(-1) ** 2; // 1
?>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);
?>funny thing
number_format(pow(2, 1023));
gives a long number
but number_format(pow(2, 1024));
gives inf