PHP implementation of simple and high-precision method of seeking Pi

This article is followed by a [PHP implementation of the dart to find the Pi method, the most stupid but most interesting] (http://www.yinqisen.cn/blog-676.html) finish the most stupid, say a more sophisticated method, the code is as follows: ~~~.php
 
  0.0000000000001) {    $z *= $a/$b;    $pi + = $z;    $b + = 2;    $a + +;} echo $pi. " \ n "; echo" PHP pi () = ". Pi ()." \ n ~ ~ ~ ~ ~ ~ ~ the source code and PHP comes with the PI () This function is compared, the accuracy is consistent, then guess how the Pi () function is implemented?

