The 4th Annual China PHP Conference


(PHP 4, PHP 5, PHP 7)

piGet value of pi


float pi ( void )

Returns an approximation of pi. The returned float has a precision based on the precision directive in php.ini, which defaults to 14. Also, you can use the M_PI constant which yields identical results to pi().

Return Values

The value of pi as float.


Example #1 pi() example

echo pi(); // 3.1415926535898
echo M_PI// 3.1415926535898

add a note add a note

User Contributed Notes 2 notes

davidduke at hotmail dot com
12 years ago
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)
hello at gmail dot com
6 months ago
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);
To Top