php pi function

1
2<?php
3echo pi(); // 3.1415926535898
4echo M_PI; // 3.1415926535898
5?>
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7

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2Pi is often usefull in con/sin/tan functions..
3
4There are also other Pi related constants.
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6These are most of them:
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10M_PI  = 3.14159265358979323846 // pi
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14// The following were added in PHP 4.0.0
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16M_PI_2 = 1.57079632679489661923 // pi/2 
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18M_PI_4 = 0.78539816339744830962 // pi/4 
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20M_1_PI = 0.31830988618379067154 // 1/pi 
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22M_2_PI = 0.63661977236758134308 // 2/pi 
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24M_SQRTPI = 1.77245385090551602729 // sqrt(pi) (Only in PHP 4.0.2+)
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26M_2_SQRTPI = 1.12837916709551257390 // 2/sqrt(pi)
27

1pi() 
2M_PI

1echo(pi()); // returns 3.1415926535898