Last 5.3 release ever available: PHP 5.3.29 - 5.3 now EOL


(PHP 4, PHP 5)

powExponential expression


number pow ( number $base , number $exp )

Returns base raised to the power of exp.


In PHP 5.6 onwards, you may prefer to use the ** operator.



The base to use


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.


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.


Example #1 Some examples of pow()


(pow(28)); // int(256)
echo pow(-120); // 1
echo pow(00); // 1

echo pow(-15.5); // PHP >4.0.6  NAN
echo pow(-15.5); // PHP <=4.0.6 1.#IND



This function will convert all input to a number, even non-scalar values, which could lead to weird results.

See Also

  • exp() - Calculates the exponent of e
  • sqrt() - Square root
  • bcpow() - Raise an arbitrary precision number to another
  • gmp_pow() - Raise number into power

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User Contributed Notes 3 notes

chris at ocportal dot com
2 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.
scott at arciszewski dot me
6 months 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.

// These two will be equivalent as of PHP 5.6.0
$x = $y ** 2;
$x = pow($y, 2);
gilthansREMOVEME at gmail dot com
7 years ago
Note that pow(0, 0) equals to 1 although mathematically this is undefined.
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