octdec
<?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;
}
?>
pi
(PHP 4, PHP 5)
pi — 円周率の値を得る
説明
float pi
( void
)
円周率の近似値を返します。返される float 値の小数点以下の 桁数は、php.ini の precision ディレクティブに依存します。デフォルトは 14 です。 また、定数 M_PI を使用することで pi() とまったく同じ結果を取得することも可能です。
返り値
円周率の値を不動小数点数で返します。
例
例1 pi() の例
<?php
echo pi(); // 3.1415926535898
echo M_PI; // 3.1415926535898
?>
add a note
User Contributed Notespi
gmail user robkohr
05-Dec-2008 11:38
05-Dec-2008 11:38
Keamos at gmail
14-Jan-2006 05:31
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
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)