pow
(PHP 4, PHP 5)
pow — Exponential expression
Parameters
-
base -
The base to use
-
exp -
The exponent
Return Values
base raised to the power of exp.
If both arguments are non-negative integers and the result can be represented
as an integer, the result will be returned with integer type,
otherwise it will be returned as a float.
Changelog
| Version | Description |
|---|---|
| 4.2.0 | No warning is emitted on errors, even if the value can't be computed. |
| 4.0.6 | The function will now return integer results if possible, before this it always returned a float result. For older versions, you may receive a bogus result for complex numbers. |
Examples
Example #1 Some examples of pow()
<?php
var_dump(pow(2, 8)); // int(256)
echo pow(-1, 20); // 1
echo pow(0, 0); // 1
echo pow(-1, 5.5); // PHP >4.0.6 NAN
echo pow(-1, 5.5); // PHP <=4.0.6 1.#IND
?>
Notes
Note:
This function will convert all input to a number, even non-scalar values, which could lead to weird results.
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Коментарии
Note that pow(0, 0) equals to 1 although mathematically this is undefined.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.
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);
?>
It is official now that you could use
<?php
2 ** 3; // 8
// instead of
pow(2, 3); // 8
?>
If you use negative numbers, you need to use brackets for using with **
<?php
-1 ** 2; // -1
(-1) ** 2; // 1
?>