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php.cn手册 发布
(PHP 4, PHP 5)
pi — 得到圆周率值
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。
圆周率(pi)的浮点近似值。
Example #1 pi() 例子
<?php
echo pi (); // 3.1415926535898
echo M_PI ; // 3.1415926535898
?>
[#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)