You want to raise a number to a power.
To raise e to a power, use exp():
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// $exp (e squared) is about 7.389 $exp = exp(2); |
To raise it to any power, use pow():
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// $exp (2^e) is about 6.58 $exp = pow( 2, M_E); // $pow1 (2^10) is 1024 $pow1 = pow( 2, 10); // $pow2 (2^-2) is 0.25 $pow2 = pow( 2, -2); // $pow3 (2^2.5) is about 5.656 $pow3 = pow( 2, 2.5); // $pow4 ( (-2)^10 ) is 1024 $pow4 = pow(-2, 10); // is_nan($pow5) returns true, because // fractional exponent of negative 2 is not a real number. $pow5 = pow(-2, -2.5); |
The built-in constant M_E is an approximation of the value of e. It equals 2.7182818284590452354. So exp($n) and pow(M_E, $n) are identical.
It’s easy to create very large numbers using exp() and pow(); if you outgrow PHP’s maximum size (almost 1.8e308), see For how to use the arbitrary precision functions.
With exp() and pow(), PHP returns INF (infinity) if the result is too large and NAN (not a number) on an error.
