pi

(PHP 4, PHP 5)

pi — 得到圆周率值

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。

返回值

圆周率（pi）的浮点近似值。

范例

Example #1 pi() 例子

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

用户评论:

[#1] hello at gmail dot com [2015-11-23 16:26:26]

You can print pi in a more complicating way. In the code bellow we save pi as a variable and print its first 4 digits.

$n = pi();

echo round ($n,4);

[#2] davidduke at hotmail dot com [2004-03-27 18:18:48]

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)