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().
The value of pi as float.
The method does not take any parameters
Example #1 pi() example
echo pi(); // 3.1415926535898
echo M_PI; // 3.1415926535898