php man page for pi

PI(3)									 1								     PI(3)

pi - Get value of pi

SYNOPSIS
       float pi (void  )

DESCRIPTION
	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(3).

RETURN VALUES
	The value of pi as float.

EXAMPLES
       Example #1

	      pi(3) example

	      <?php
	      echo pi(); // 3.1415926535898
	      echo M_PI; // 3.1415926535898
	      ?>

PHP Documentation Group 														     PI(3)