pi

说明

float pi ( void )

返回圆周率的近似值。返回值的 float 精度是由 php.ini 中的 precision 指令确定。默认值是 14。你也可以使用 M_PI 常量，该常量产生与 pi() 完全相同的结果。

例子 1. pi()
<?php echo pi(); // 3.1415926535898 echo M_PI; // 3.1415926535898 ?>

add a note User Contributed Notes

Keamos at gmail
14-Jan-2006 01:31


For anyone wondering, the highest precision you can get for pi() or M_PI is 20 places after the decimal point, or 3.14159265358979323846.

davidduke at hotmail dot com
28-Mar-2004 10:18


Pi is often usefull in con/sin/tan functions..


There are also other Pi related constants.


These are most of them:





M_PI  = 3.14159265358979323846 // pi





// The following were added in PHP 4.0.0


M_PI_2 = 1.57079632679489661923 // pi/2 


M_PI_4 = 0.78539816339744830962 // pi/4 


M_1_PI = 0.31830988618379067154 // 1/pi 


M_2_PI = 0.63661977236758134308 // 2/pi 


M_SQRTPI = 1.77245385090551602729 // sqrt(pi) (Only in PHP 4.0.2+)


M_2_SQRTPI = 1.12837916709551257390 // 2/sqrt(pi)

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