(PHP 4, PHP 5, PHP 7, PHP 8)
pow — Exponential expression
Returns num raised to the power of
exponent.
Зауваження:
It is possible to use the ** operator instead.
numThe base to use
exponentThe exponent
num raised to the power of exponent.
If both arguments are non-negative integers and the result can be represented
as an integer, the result will be returned with int type,
otherwise it will be returned as a float.
PHP-Extensions may override the behaviour of this operation and make it return an object.
Приклад #1 Some examples of pow()
<?php
var_dump(pow(2, 8)); // int(256)
echo pow(-1, 20), PHP_EOL; // 1
echo pow(0, 0), PHP_EOL; // 1
echo pow(10, -1), PHP_EOL; // 0.1
var_dump(pow(new GMP("3"), new GMP("2"))); // object(GMP)
echo pow(-1, 5.5); // NAN
?>Зауваження:
This function will convert all input to a number, even non-scalar values, which could lead to weird results.
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);
?>