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# pi

(PHP 4, PHP 5)

piВозвращает число Пи

### Описание

float pi ( void )

Возвращает число Пи с точностью, определяемой директивой precision в php.ini, значение по умолчанию которой 14. Константа M_PI даёт идентичный результат.

Пример #1 Пример pi()

`<?phpecho pi(); // 3.1415926535898echo M_PI; // 3.1415926535898?>`

User Contributed Notes
pi
ghostt dot ew at gmail dot com
10-Feb-2010 12:05
```The highest current precision you can get from pi() at this point is 49 digits. <?php \$precision = 49; ini_set("precision", \$precision); echo pi(); //will output 3.141592653589793115997963468544185161590576171875 ?>```
gmail user robkohr
05-Dec-2008 11:38
```<?php /*  Returns angle of line segment in degrees. Angle will be a positive  value between 0 and 360. 0 will be north, 90 east, 180 south, 270 west  Author: Robert Kohr */ function get_angle(\$x1, \$y1, \$x2, \$y2, \$negative_y_is_up=0){   //differences in x and y   \$x = \$x2 - \$x1;   \$y = \$y2 - \$y1;   //y will need to be negated for where + y is down   if(\$negative_y_is_up){     //useful in some applications     \$y = -\$y;   }   return (rad2deg(atan2(\$x, \$y))+360)%360; } ?>```
Keamos at gmail
14-Jan-2006 05:31
`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 02:18
```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)```