pi

Returns the value of PI to 14 (default) decimal places. This precision can be altered in the php.ini file.

PHP

echo pi();
// => 3.1415926535898

Ruby

puts Math::PI;
# => 3.14159265358979

In the code above, PI is actually a constant of the Module Math. PHP also has a constant which stores the approximate value of PI - M_PI.

PHP

echo M_PI();
// => 3.1415926535898