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.